Mexican food: donkey fed with it (7)
I believe the answer is:
burrito
'mexican food' is the definition.
(I've seen this before)
'donkey fed with it' is the wordplay.
'donkey fed' becomes 'burro' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' means one lot of letters goes inside another.
'burro' going around 'it' is 'BURRITO'.
Can you help me to learn more?
(Other definitions for burrito that I've seen before include "Tortilla folded round a filling" , "Mexican dish of tortilla folded around a filling" , "Mexican dish - rub trio (anag)" , "Tortilla folded around a savoury filling" , "Filled tortilla dish" .)