Piece of tortilla served with sauce (5)
I believe the answer is:
nacho
'piece of tortilla served with sauce' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for nacho that I've seen before include "Tortilla crisp" , "kind of chip" , "Mexican tortilla chip" , "Hot snack" , "chip production line unit" .)