Be sold in greater quantities than (7)
I believe the answer is:
outsell
'be sold in greater quantities than' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for outsell that I've seen before include "Get more buyers than the competition" , "conquer in the market" , "Retail better than" , "Be sold in greater quantities than" , "(Of a commodity) attract more customers than" .)