The dog for a pugilist (5)
I believe the answer is:
boxer
I believe this clue is a double definition.
'the dog' is the first definition.
(boxer is a kind of dog)
'for a pugilist' is the second definition.
(synonyms)
(Other definitions for boxer that I've seen before include "Prizefighter" , "Asian rebel" , "Dog - fighter" , "canine" , "Pugilist - dog" .)