Burger topping (6)
I believe the answer is:
pickle
'burger topping' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pickle that I've seen before include "Chutney, relish, salsa etc" , "Immerse (object) in acid" , "Relish; predicament" , "Solution for preserving food" , "Awkward situation" .)