Infantryman rereading novel (9)
I believe the answer is:
grenadier
'infantryman' is the definition.
(I know that grenadier is a type of infantryman)
'rereading novel' is the wordplay.
'novel' is an anagram indicator (letters in a new or novel order).
'rereading' with letters rearranged gives 'GRENADIER'.
(Other definitions for grenadier that I've seen before include "Infantryman - in red gear (anag)" , "guard" , "Soldier - in red gear (anag)" , "historical bomber" , "Re-reading for the deep-sea fish" .)