What chef did outside recipe is not kosher (7)
I believe the answer is:
crooked
'not kosher' is the definition.
(thesaurus)
'what chef did outside recipe' is the wordplay.
'what chef did' becomes 'cooked'.
'outside' means one lot of letters goes inside another.
'recipe' becomes 'r' (abbreviation).
'cooked' enclosing 'r' is 'CROOKED'.
'is' is the link.
(Other definitions for crooked that I've seen before include "Misshapen" , "Bent, twisted" , "Awry - untrustworthy" , "Not straight or aligned" , "Bent; dishonest" .)