Jargon surrounding cooker contract (8)
I believe the answer is:
covenant
'contract' is the definition.
(covenanting is a kind of contracting)
'jargon surrounding cooker' is the wordplay.
'jargon' becomes 'cant' (synonyms).
'surrounding' means one lot of letters goes inside another.
'cooker' becomes 'oven' (synonyms).
'cant' placed around 'oven' is 'COVENANT'.
(Other definitions for covenant that I've seen before include "Binding agreement between two parties" , "pledge" , "Contract made in a convent" , "Signed agreement between two or more to do something" , "Concordat, compact" .)