Eats quickly in barracks (6)
I believe the answer is:
scoffs
This clue could be a double definition.
'eats quickly' is the first definition.
'scoffs' can be an answer for 'eats' (I've seen this before). I am not sure about the 'quickly' bit.
'barracks' is the second definition.
('scoff' can be a synonym of 'barrack')
'in' is the link.
Can you help me to learn more?
(Other definitions for scoffs that I've seen before include "Jeers or drinks up" , "Abandons diet" , "Laughs at the idea of" , "'Jeers, scorns (6)'" , "Mocks or drinks greedily" .)