Comes up, as about a pay increase (6)
I believe the answer is:
arises
'comes up' is the definition.
('arise' can be a synonym of 'come up')
'as about a pay increase' is the wordplay.
'about' means one lot of letters goes inside another.
'a pay increase' becomes 'rise' (I've seen this before).
'as' placed around 'rise' is 'ARISES'.
(Other definitions for arises that I've seen before include "Comes to notice, like committee business" , "Gets up or comes up" , "Gets out of bed" .)