Margarita garnish (4)
I believe the answer is:
'margarita garnish' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lime that I've seen before include "Round green fruit or a linden tree" , "Sharp-tasting fruit" , "Having no money" , "White substance used in cement" , "Yellowish-green" .)