Moisten with hot fat (5)
I believe the answer is:
baste
'moisten with hot fat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for baste that I've seen before include "Moisten with hot fat" , "Keep moisturised when baking" , "Moisten with liquid fat while roasting" , "Moisten roasting meat with melted fat" , "Pour fat over meat during cooking" .)