Devour in one attempt (3)
I believe the answer is:
eat
'devour' is the definition.
(I've seen this before)
'in one attempt' is the wordplay.
'in' says the answer is hidden in the clue.
'EAT' is hidden in the letters of 'one attempt'.
(Other definitions for eat that I've seen before include "Be corrosive" , "Devour" , "Take food" , "Worry" , "get stuck in" .)