Reduction in price for salad vegetable (3)
I believe the answer is:
cos
'salad vegetable' is the definition.
(type of lettuce)
'reduction in price' is the wordplay.
'reduction in' means to remove the last letter (the number of letters in the word is reduced).
'price' becomes 'cost' (synonyms).
'cost' with its last letter taken off is 'COS'.
'for' acts as a link.
(Other definitions for cos that I've seen before include "in the Dodecanese?" , "Salad ingredient" , "Senior officers" , "Variety of lettuce" , "providing unsatisfactory explanation?" .)