Add pounds in wage increase overseen by a polymath (9)
I believe the answer is:
aristotle
'polymath' is the definition.
(I've seen this before)
'add pounds in wage increase overseen by a' is the wordplay.
'add' becomes 'tot' (synonyms).
'pounds' becomes 'L' (L can represent the monetary pound).
'in' means one lot of letters goes inside another.
'wage increase' becomes 'rise'.
'overseen by' says to put letters next to each other (in a down clue, some letters go above others).
'tot'+'l'='totl'
'totl' inserted within 'rise' is 'ristotle'.
'ristotle' after 'a' is 'ARISTOTLE'.
(Other definitions for aristotle that I've seen before include "Greek logician" , "Ancient Greek philosopher" , "Greek philosopher, pupil of Plato, tutor of Alexander the Great" , "polymath" , "Greek philosopher (Poetics, Politics)" .)