BLT condiment (4)
I believe the answer is:
mayo
'blt condiment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mayo that I've seen before include "You'll find it in the Emerald Isle" , "Irish county - sauce (abbr)" , "Thick creamy dressing" , "Irish county (county town, Castlebar)" , "County of north-west Ireland" .)