Parched, drinking cold bitter (5)
I believe the answer is:
acrid
'bitter' is the definition.
(I've seen this before)
'parched drinking cold' is the wordplay.
'parched' becomes 'arid' (I've seen this before).
'drinking' is an insertion indicator (inserted letters are consumed or drunk).
'cold' becomes 'c' (eg on taps).
'arid' placed around 'c' is 'ACRID'.
(Other definitions for acrid that I've seen before include "Sharp - biting" , "causing corrosion" , "Nastily pungent" , "Bitterly pungent" , "Having a bitter smell or taste" .)