Bitter cold, very dry outside (5)
I believe the answer is:
acrid
'bitter' is the definition.
(thesaurus)
'cold very dry outside' is the wordplay.
'cold' becomes 'c' (eg on taps).
'very dry' becomes 'arid' (I've seen this before**).
'outside' means one lot of letters goes inside another.
'c' put inside 'arid' is 'ACRID'.
(Other definitions for acrid that I've seen before include "Stinging" , "Sour, pungent" , "Strong and sharp-smelling" , "Unpleasantly bitter" , "Having a bitter smell or taste" .)