Crop that's a bargain (4)
I believe the answer is:
snip
I believe this is a double definition.
'crop' is the first definition.
('snip' can be a synonym of 'crop')
'a bargain' is the second definition.
(slang term for a good deal)
'that's' acts as a link.
(Other definitions for snip that I've seen before include "Easy to do - use pins" , "Something cheap or easy to do" , "bargain buy" , "Bargain (coll)" , "Cut - price bargain" .)