Office temp's initial depression (4)
I believe the answer is:
Here is my best explanation:
'depression' is the definition.
(dent is a kind of depression)
'office temp's initial' is the subsidiary indication.
'office' becomes 'den' (I've seen this in other clues).
'initial' suggests taking the first letters.
The initial letter of 'temp' is 't'.
(Other definitions for dent that I've seen before include "Hollow, depression", "Tend to small indentation", "Slight damage", "Small hollow", "Surface hollow", "Injury to pride", "Small depression", "Hollow; tend (anagram)", "Hollow caused by a blow" and "Tend (anag.)".)