Thief finally confronted over coffee (6)
I believe the answer is:
decaff
'coffee' is the definition.
(I've seen this before)
'thief finally confronted over' is the wordplay.
'finally' indicates one should take the final letters.
'confronted' becomes 'faced' ('face' can be a synonym of 'confront').
'over' is a reversal indicator.
The last letter of 'thief' is 'f'.
'f'+'faced'='ffaced'
'ffaced' backwards is 'DECAFF'.
(Other definitions for decaff that I've seen before include "Coffee without the kick" , "Type of coffee (colloq.)" .)