Rereading about soldier (9)
I believe the answer is:
grenadier
'soldier' is the definition.
(historical term for a grenade-carrying soldier)
'rereading about' is the wordplay.
'about' indicates an anagram.
'rereading' is an anagram of 'GRENADIER'.
(Other definitions for grenadier that I've seen before include "African flier" , "Infantryman - in red gear (anag)" , "guard" , "bomb-thrower" , "A household infantryman" .)