Liquid for soaking food before cooking (8)
I believe the answer is:
marinade
'liquid for soaking food before cooking' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for marinade that I've seen before include "Soak in a mixture before cooking" , "Type of star system" , "Mixture for soaking foods before cooking" , "Spicy liquid for soaking meat or fish" , "Food is steeped in this to improve flavour" .)