Mephisto 3040 by Don Manley

This was a very pleasant puzzle of average complexity. I have minor parsing queries at 20A and 24D. (On Edit: now cleared up in the comments) Quite a smattering of GK required and two London Boroughs clued as something else.

In the clues, definitions are underlined. Wordplay explanation is followed by very helpful comments.

ACROSS

1 Certain trees — a number falling over in very high winds (8)
GNETALES: G(TEN reversed)ALES; gymnosperms that possess some angiosperm‐like features.
11 A feudal superior’s right to leave estate (4)
ALOD: A-LO(r)D; Land held by right of freehold (Doomsday Book)
12 One paper with a new retro-looking script (6)
NAGARI: I-RAG-A-N all reversed; a writing system used in India and Nepal.
13 Dweller in hot zone, possibly Indian, catching cold (6)
ASCIAN: AS(C)IAN; a person who lives in the area between the tropics
14 Artistic fabric not unknown in arrangements (5)
ARRAS: ARRA(y)S; a wall hanging made of a rich tapestry fabric
15 Bigwig entertaining children may limit possibility of seeing adult material (5)
V-CHIP: V(CH)IP; a technology used in television set receivers in Canada, Brazil and the United States, that allows the blocking of programs based on their ratings category. It is intended for use by parents to manage their children’s television viewing.
16 Firm supports pirates? (7)
COPIERS: CO-PIERS; to pirate is to make illegal copies
18 This writer’s teaching qualification is seen as fix (5)
IMBED: I’M-BED; B Ed=Bachelor of Education; alternative spelling of “embed”
20 Keep walking, making wrong movement through water (8)
TRUDGEON: TRUDGE-ON; The trudgen is a swimming stroke sometimes known as the racing stroke, or the East Indian stroke. It is named after the English swimmer John Trudgen and evolved out of sidestroke. I have no idea why it’s “wrong”
23 Mathematical function, doubly special, conveys a nice feeling (8)
COSINESS: COSINE-S-S; Oh, wouldn’t that be loverly!
25 Rock includes old musical instrument (5)
SAROD: SAR(O)D; a stringed instrument, used mainly in Hindustani music
28 Farmer’s annoyance after grain is minimal (7)
GRANGER: GR(ain)-ANGER;
29 Beloved from Scotland, burning with inner energy (5)
LIEVE: LI(E)VE;
30 One having freedom from recrimination, little devil getting off (5)
UNITY: (imp)UNITY;
31 Pole’s getting nothing in a strange land (6)
ANODAL: A-(land)* surrounds O; an anode is the positively charged electrode by which electrons leave an electrical device.
32 Repair what is left, implanting gold (6)
RESORT: RES(OR)T;
33 Passage of Islamic writing rejecting extreme members (4)
ADIT: (h)ADIT(h); opening into a mine;
34 Climber taking a path ere collapsing (8)
HEARTPEA: (a path ere)*; Cardiospermum or heartseed;

DOWN

1 Importance of life in lawn area that’s been cut (8)
GRAVITAS: GRA(VITA)S(s);
2 An upsetting blemish in one form of motor racing (6)
NASCAR: AN reversed – SCAR; National Association for Stock Car Auto Racing
3 Greek character undermining the Spanish ambassador (5)
ELCHI: EL-CHI; A Turkish ambassador
4 Modify notice, adding a short point (5)
ADAPT: AD-A-PT;
5 Uncle with no teeth, sloppy diner (12)
LUNCHEONETTE: (uncle no teeth)*; a small, informal restaurant serving light lunches.
6 Old group of animals comes to a tarn to be refreshed (12)
ENTOMOSTRACA: (comes to a tarn)*; a historical subclass of crustaceans, no longer in technical use
7 Plant suffering around outermost part (8)
AGRIMONY: AG(RIM)ONY; perennial herbaceous flowering plants
8 Protection against many a wild animal, a zebra possibly? (6)
ZAREBA: (a zebra)*; a thorn fence fortifying a camp or village
9 Vessels collide briefly — engineers brought aboard (6)
CRARES: CRA(RE)S(h); old trading ships
10 Geological stage poses dangers — rock finally crumbles away (4)
RISS: RIS(k)S; The Glacial Stage during which Alpine glaciers descended from the highlands. It followed the Mindel-Riss Interglacial Stage and preceded the Riss-Würm Interglacial Stage
17 Men do not get drunk in North American city (8)
EDMONTON: (men do not)*; capital of Canada’s Alberta province (also a district in North London)
19 Limb problem, mild and easy to put right (8)
DYSMELIA: (mild easy)*; congenital disorder of a limb resulting from a disturbance in embryonic development
21 Hairstyle? Sir needs a bit removed from the middle (6)
BARNET: BAR(o)NET; CRS for hair or hair style (Barnet Fair) – another district in North London
22 A pithy expression said to create commotion (6)
FRAISE: sounds like “phrase”;
24 Cruel person had for a time a pugilistic style (6)
SAVATE: cruel person=savage then change “g” to “t=time” (I don’t quite understand the wordplay); a French form of boxing that uses the hands and feet as weapons
26 Disrespectful narrative — some of it near the bone (5)
ULNAR: hidden (disrespectf)UL-NAR(rative); bone in the wrist close to the ulna
27 Princess wearing material that’s clean again? (5)
REDIP: RE(DI)P; material=REP;
28 Sound of lass making rough noise (4)
GURL: sounds like “girl”; to growl in the Grampians