Cook's bipolar disorder (7)
I believe the answer is:
parboil
'cook's' is the definition.
(parboiling is a kind of cooking)
'bipolar disorder' is the wordplay.
'disorder' is an anagram indicator (a disordered version of the letters).
'bipolar' anagrammed gives 'PARBOIL'.
(Other definitions for parboil that I've seen before include "Simmer food until partly cooked" , "Cook a little" , "Partially cook" , "Half-cook" , "Cook in hot water briefly" .)