Employed and also working under king (4,2)
I believe the answer is:
took on
'employed' is the definition.
(I've seen this before)
'also working under king' is the wordplay.
'also' becomes 'too' (synonyms).
'working' becomes 'on' (on can mean working or activated).
'under' says to put letters next to each other (in a down clue, some letters go below others).
'king' becomes 'K' (chess abbreviation).
'on' after 'k' is 'kon'.
'too'+'kon'='TOOK ON'
'and' acts as a link.
(Other definitions for took on that I've seen before include "Employed" , "challenged" , "Got upset < , did recruit" .)