Basil-and-pine-nuts sauce (5)
I believe the answer is:
pesto
'basil-and-pine-nuts sauce' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pesto that I've seen before include "sauce involving Basil" , "Basic sauce" , "Sauce made of basil and cheese" , "Pasta sauce based on basil" , "Sauce of basil, pine nuts, etc" .)