Secretary getting unknown remuneration (3)
I believe the answer is:
pay
'remuneration' is the definition.
(synonyms)
'secretary getting unknown' is the wordplay.
'secretary' becomes 'PA' (abbreviation for personal assistant).
'getting' says to put letters next to each other.
'unknown' becomes 'y' (algebra).
'pa'+'y'='PAY'
(Other definitions for pay that I've seen before include "Profit" , "Settle up" , "Hand over money for" , "Earnings" , "Money for work" .)