Petition concerning hunt (7)
I believe the answer is:
request
'petition' is the definition.
(synonyms)
'concerning hunt' is the wordplay.
'concerning' becomes 're'.
'hunt' becomes 'quest' (quest is a kind of hunt).
're'+'quest'='REQUEST'
(Other definitions for request that I've seen before include "bidding" , "Call for" , "Polite demand" , "Appeal" , "Suit" .)