Vinegar acid (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
acetic
'vinegar acid' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for acetic that I've seen before include "really sour" , "Like the acid in vinegar" , "sort of acid" , "tart" , "Saucy'" .)