Spectator 2023

[Nical]

I've just 25 Across to get...
Tree surgeon's ultimate doctor (4) n?mb
I've searched through my dictionary and can't see anything appropriate. Any ideas?

[dr b]

The missing letter is not indicated by the wordplay, so it's going to be part of the "another member of the thematic group"; so that should give you the letter once you have the missing "member".

The answer is an alternate spelling of "A tree, Azadirachta indica (family Meliaceae), widely found in South Asia, where it is valued for its leaves and bitter bark which are used medicinally, and for the oil of its seeds which is used in soaps."

[ironmonger]

If your N is wrong it could be LIMB

[Nical]

Thanks, both of you.
Ironmonger - for ages I thought 'limb' was the answer, but a Dwn clue is correct, so the 'n' is too!
Dr b - I think I know the tree you mentioned,it came up when I was trying out 'n?m?' (when I thought maybe my 'b' was wrong).
Even though I've solved this all bar 25 A, the preamble looked so daunting that I decided not to attempt it just yet.

[dr b]

But surely if you've solved all but 25a, you've noticed at least some of the missing letters from wordplay; if you highlight these you should see a pattern forming.

[Nical]

Totally finished now -I had only two of the missing letters so it took me a while (and I was looking in the wrong place initially).

[mathsman]

Can't reconcile 6th letter of 36a (m) with 5th letter of 26d (n).

Any tips, please.

[Ironie]

The mantra referred to is 'OM', okay?