Grant it’s cold once December starts (7)
I believe the answer is:
concede
'grant' is the definition.
(I know that grant can be written as concede)
'cold once december starts' is the wordplay.
'cold' becomes 'c' (eg on taps).
'december' becomes 'Dec' (synonyms).
'starts' means to remove the last letter.
'dec' with its final letter taken away is 'de'.
'c'+'once'+'de'='CONCEDE'
'it's' acts as a link.
(Other definitions for concede that I've seen before include "Admit (defeat in match)" , "Surrender, yield" , "Make admission" , "Acknowledge defeat" , "Yield; grant" .)