First to play apart (5)
I believe the answer is:
aside
'apart' is the definition.
(synonyms)
'first to play' is the wordplay.
'first' becomes 'a'.
'to play' becomes 'side' (I can't explain this - if you can you should believe this answer much more).
'a'+'side'='ASIDE'
Can you help me to learn more?
(Other definitions for aside that I've seen before include "Line spoken to the audience of a play" , "(Pushed) out of the way" , "Remark by an actor, directly to audience say" , "Ideas (anag)" , "Actor's line directed solely to audience" .)