Heathen in field wounded (7)
I believe the answer is:
infidel
'heathen' is the definition.
(synonyms)
'in field wounded' is the wordplay.
'wounded' is an anagram indicator.
'field' with letters rearranged gives 'fidel'.
'in'+'fidel'='INFIDEL'
(Other definitions for infidel that I've seen before include "Disbeliever" , "One who doesn't believe" , "Person who has no faith, or the wrong one" , "One without religion (mainly archaic)" , "Person who rejects a religious belief" .)