Devour in one attempt (3)
I believe the answer is:
Here is my best explanation:
'devour' is the definition.
(I've seen this before)
'in one attempt' is the subsidiary indication.
'in' indicates a hidden word.
'eat' is hidden in the letters of 'one attempt'.
(Other definitions for eat that I've seen before include "Do cats - bats? Do bats - cats? (Alice in Wonderland)", "Put away", "tolerate in diet", "Dine in a restaurant", "Take food", "get stuck in", "Partake of", "Feed", "Have a meal" and "Consume (food)".)