Mexican snack requires some spinach, occasionally (5)
I believe the answer is:
'mexican snack' is the definition.
(I've seen this before)
'some spinach occasionally' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'NACHO' is hidden within 'spinach occasionally'.
'requires' is the link.
(Other definitions for nacho that I've seen before include "Nibble" , "kind of chip" , "Mexican dish" , "Mexican snack item" , "Mexican corn chip eaten with cheese, etc" .)