Bitter about cold search (5)
I believe the answer is:
scour
'search' is the definition.
(I know that scour is a type of search)
'bitter about cold' is the wordplay.
'bitter' becomes 'sour' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'cold' becomes 'c' (eg on taps).
'sour' enclosing 'c' is 'SCOUR'.
(Other definitions for scour that I've seen before include "purge" , "flush out" , "Clean by abrasion" , "Hunt through" , "Attack with brush" .)