Thanks company for Mexican snack (4)
I believe the answer is:
taco
'mexican snack' is the definition.
(I've seen this before)
'thanks company' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'company' becomes 'co' (abbreviation).
'ta'+'co'='TACO'
'for' is the link.
(Other definitions for taco that I've seen before include "foreign food" , "quick dish" , "Mexican filled pancake" , "Filled, fried tortilla" , "Filled tortilla roll" .)