Study time of damage (4)
I believe the answer is:
dent
'damage' is the definition.
(dent is a kind of damage)
'study time' is the wordplay.
'study' becomes 'den' (term for a study or office).
'time' becomes 't' (abbreviation).
'den'+'t'='DENT'
'of' is the link.
(Other definitions for dent that I've seen before include "TV lexicographer?" , "northern banker" , "Tend (anag.)" , "'Dinge, depression (4)'" , "Hollow caused by a blow" .)