Attempt; exhausted (4)
I believe the answer is:
shot
This clue is a double definition.
'attempt' is the first definition.
(shot is a kind of attempt)
'exhausted' is the second definition.
(I've seen this in another clue)
(Other definitions for shot that I've seen before include "Photo; lead pellets" , "Charge" , "completely gone" , "Darted" , "Fired; (be) rid (of)" .)