Old soldier re-reading novel (9)
I believe the answer is:
grenadier
'old soldier' is the definition.
'grenadier' can be an answer for 'soldier' (historical term for a grenade-carrying soldier). I am not sure about the 'old' bit.
're-reading novel' is the wordplay.
're-reading' becomes 'rereading' ('reread' can be a synonym of 're-read').
'novel' is an anagram indicator (letters in a new or novel order).
'rereading' with letters rearranged gives 'GRENADIER'.
Can you help me to learn more?
(Other definitions for grenadier that I've seen before include "bomb-thrower" , "historical bomber" , "guard" , "Soldier - in red gear (anag)" , "A household infantryman" .)