Sonora snack (4)
I believe the answer is:
taco
'sonora snack' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for taco that I've seen before include "Set of three" , "Tortilla with savoury filling" , "Mexican filled tortilla" , "Coat with Mexican dish" , "Mexican food" .)