Cook swallows fish without coercion (6)
I believe the answer is:
freely
'without coercion' is the definition.
(thesaurus)
'cook swallows fish' is the wordplay.
'cook' becomes 'fry' (fry cook is a kind of cook).
'swallows' means one lot of letters goes inside another.
'fish' becomes 'eel' (eel is a type of fish).
'fry' placed around 'eel' is 'FREELY'.
(Other definitions for freely that I've seen before include "boldly" , "in copious quantities" , "Without restriction or payment" , "Without compulsion" , "easily" .)