Also accepted king must leave (3)
I believe the answer is:
too
'also' is the definition.
(I know that also can be written as too)
'accepted king must leave' is the wordplay.
'accepted' becomes 'took' (take can mean to accept something).
'king' becomes 'K' (abbreviation for king in chess).
'must leave' indicates named letters should be taken away.
'took' with 'k' taken out is 'TOO'.
(Other definitions for too that I've seen before include "Likewise" , "As well; in addition" , "On top - also" , "As well, also" , "To a greater than desirable extent" .)