Expert attempt (5)
I believe the answer is:
crack
This clue is a double definition.
'expert' is the first definition.
(as in 'a crack team')
'attempt' is the second definition.
(crack is a kind of attempt)
(Other definitions for crack that I've seen before include "Fracture" , "Break sharply; a joke" , "Take severe measures - . . . . . down on" , "Go for expert" , "Opening; sharp blow" .)