Whistle-blower returning holding gun for yeoman (6)
I believe the answer is:
farmer
'yeoman' is the definition.
(thesaurus)
'whistle-blower returning holding gun' is the wordplay.
'whistle blower' becomes 'ref' (a referee blows a whistle).
'returning' shows that the letters should be reversed in order.
'holding' is an insertion indicator.
'gun' becomes 'arm' (I've seen this in other clues).
'ref' back-to-front is 'fer'.
'fer' enclosing 'arm' is 'FARMER'.
'for' acts as a link.
(Other definitions for farmer that I've seen before include "One cultivating land" , "He lives off the land" , "One who cultivates land" , "Cultivator" , "Agriculturist" .)