Nut turned up in endlessly dry and primarily arid, treeless region (6)
I believe the answer is:
tundra
'treeless region' is the definition.
(I've seen this in another clue)
'nut turned up in endlessly dry and primarily arid' is the wordplay.
'turned' says the letters should be written backwards.
'up in' becomes 'd' (I can't explain this - if you can you should believe this answer much more).
'endlessly' says to take the centre (the ends of the words are removed).
'and' means one lot of letters go next to another.
'primarily' suggests taking the first letters.
The central letter of 'dry' is 'r'.
The first letter of 'arid' is 'a'.
'nut' back-to-front is 'tun'.
'tun'+'d'+'r'+'a'='TUNDRA'
Can you help me to learn more?
(Other definitions for tundra that I've seen before include "Northern permafrost region" , "Area of permafrost" , "Cold plain" , "Treeless frozen Arctic plain" , "Sub-polar treeless zone" .)