Wounded grenadier is studying again (9)
I believe the answer is:
rereading
'studying again' is the definition.
('reading' can be a synonym for 'studying' so perhaps 'rereading' is OK for 'studying again')
'wounded grenadier' is the wordplay.
'wounded' indicates an anagram (I've seen this in other clues).
'grenadier' with letters rearranged gives 'REREADING'.
'is' is the link.
(Other definitions for rereading that I've seen before include "Perusing again" , "Grenadier (anag.)" , "looking at things again" .)