Sell cheaper than the competition (8)
I believe the answer is:
undercut
'sell cheaper than the competition' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for undercut that I've seen before include "As a business person try to outmanoeuvre" , "Slice below or lower prices" , "Sell for less than (rival)" , "Offer a better price than (a competitor)" , "Sell for lower price than another" .)