Sauce made quickly without recipe (5)

I believe the answer is:

pesto

I'm a little stuck... Click here to teach me more about this clue!

'sauce' is the definition.
(pesto is a type of sauce)

I cannot understand how the remainder of the clue works.

(Other definitions for pesto that I've seen before include "Green sauce" , "Pasta sauce mainly of basil and cheese" , "Basic sauce" , "Italian sauce containing basil" , "Basil-based sauce" .)

I've seen this clue in the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app