Quiet force keeps returning fire for officer (7)
I believe the answer is:
sheriff
'officer' is the definition.
(thesaurus)
'quiet force keeps returning fire' is the wordplay.
'quiet' becomes 'sh' (**).
'force' becomes 'f' (symbol used in Physics e.g. f=ma).
'keeps' is an insertion indicator.
'returning' shows that the letters should be reversed in order.
'fire' written backwards gives 'erif'.
'sh'+'f'='shf'
'shf' going around 'erif' is 'SHERIFF'.
'for' is the link.
(Other definitions for sheriff that I've seen before include "Crown's chief executive in a county" , "County official" , "US law enforcement officer" , "Chief Crown representative in a county" , "US county law enforcer" .)