An advantage and more (4)
I believe the answer is:
plus
This clue is a triple definition!
'an advantage' is the first definition.
(a plus is an advantage or benefit)
'and' is the second definition.
'more' is the third definition.
(I've seen this before)
(Other definitions for plus that I've seen before include "And also; a bonus" , "credit" , "An advantage (colloq.)" , "Positive and not a negative" , "Coupled with" .)