Chihuahua chow (4)
I believe the answer is:
'chihuahua chow' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for taco that I've seen before include "Mexican filled pancake" , "Folded and filled tortilla" , "Coat with Mexican dish" , "Filled tortilla roll" , "Tortilla rolled round a filling" .)