Exceptional grant and a fourth armed man? (9)
I believe the answer is:
dartagnan
'fourth armed man?' is the definition.
(fourth character in The Three Musketeers)
'exceptional grant and a' is the subsidiary indication.
'exceptional' is an anagram indicator.
'grant'+'and'+'a'='grantanda'
'grantanda' with letters rearranged gives 'dartagnan'.
(Other definitions for dartagnan that I've seen before include "French hero ..." , "Front of advancing army" , "Hero of The Three Musketeers" , "Hero of Les Trois Mousquetaires (Dumas)" , "Novel hero" .)