The fellow leading soldiers up -- a courageous man (4)
I believe the answer is:
hero
'a courageous man' is the definition.
(I've seen this before)
'the fellow leading soldiers up' is the wordplay.
'the fellow' becomes 'he' (pronoun for a man).
'leading' is a charade indicator (letters next to each other).
'soldiers' becomes 'OR' (Other Ranks).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'or' written backwards gives 'ro'.
'he'+'ro'='HERO'
(Other definitions for hero that I've seen before include "Star" , "victor" , "Book's chief character" , "Brave guy" , "Principal character in a film or novel" .)