Study temperature of hollow (4)
I believe the answer is:
dent
'hollow' is the definition.
(I've seen this before)
'study temperature' is the wordplay.
'study' becomes 'den' (I've seen this before).
'temperature' becomes 't' (abbreviation).
'den'+'t'='DENT'
'of' is the link.
(Other definitions for dent that I've seen before include "Injury to pride" , "Slight damage" , "Impression left by impact" , "Small hollow" , "Notch" .)