Salad ingredient at reduced cost? (3)
I believe the answer is:
cos
'salad ingredient' is the definition.
(type of lettuce)
'reduced cost?' is the wordplay.
'reduced' means to remove the last letter.
'cost' with its final letter taken away is 'COS'.
'at' acts as a link.
(Other definitions for cos that I've seen before include "holiday destination" , "A long-leaved lettuce" , "leaves > function" , "naturally having longer leaves than most" , "Senior officers" .)