Popular setter secures right to get pay rise (9)
I believe the answer is:
increment
'pay rise' is the definition.
(an incremental increase in pay)
'popular setter secures right' is the wordplay.
'popular' becomes 'in'.
'setter' becomes 'cement' (something that sets).
'secures' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'cement' enclosing 'r' is 'crement'.
'in'+'crement'='INCREMENT'
'to get' acts as a link.
(Other definitions for increment that I've seen before include "Amount by which something increases" , "Small change" , "Small addition to salary etc" , "additional pay" , "Increase (one of a series)" .)