Poor salesmen had left out wholesale (2,5)
I believe the answer is:
en masse
'wholesale' is the definition.
(both can mean as a group)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for en masse that I've seen before include "In force" , "In a group U altogether" , "in concert" , "Sees man (anag.)" , "Many as one" .)