A sort mixed for cook (5)
I believe the answer is:
roast
'for cook' is the definition.
(roasting is a kind of cooking)
'a sort mixed' is the wordplay.
'mixed' indicates an anagram.
'a'+'sort'='asort'
'asort' with letters rearranged gives 'ROAST'.
(Other definitions for roast that I've seen before include "Have a go at" , "burn?" , "pan" , "Become very warm" , "Cooked meat; criticise" .)