Price reduced for lettuce (3)
I believe the answer is:
cos
'for lettuce' is the definition.
(cos is a kind of lettuce)
'price reduced' is the wordplay.
'price' becomes 'cost' (synonyms).
'reduced' means to remove the last letter.
'cost' with its final letter removed is 'COS'.
(Other definitions for cos that I've seen before include "providing unsatisfactory explanation?" , "Salad ingredient" , "Senior officers" , "holiday destination" , "Greek island (alternative spelling): Trig abbrev!" .)