Consume in one attempt (3)
I believe the answer is:
Here is my best explanation:
'consume' is the definition.
(eating is a kind of consuming)
'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)", "Break bread", "Bit, chew and swallow", "Consume for tea", "Munch", "Consume (food)", "Use a knife and fork", "Corrode", "Partake of" and "Bite, chew and swallow".)