Contention put side off (7)
I believe the answer is:
dispute
'contention' is the definition.
(thesaurus)
'put side off' is the wordplay.
'off' indicates anagramming the letters.
'put'+'side'='putside'
'putside' with letters rearranged gives 'DISPUTE'.
(Other definitions for dispute that I've seen before include "Question or deny accuracy or validity" , "Disagree or challenge" , "Row" , "Argument, contention" , "Argue about (something)" .)