Leading player on time for opening (5)
I believe the answer is:
start
'for opening' is the definition.
(both can mean the beginning)
'leading player on time' is the wordplay.
'leading player' becomes 'star' (I've seen this in another clue).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'time' becomes 't' (abbreviation).
'star'+'t'='START'
(Other definitions for start that I've seen before include "begin an argument?" , "Begin; flinch" , "Begin - opening move" , "Move quickly < when surprised" , "Initiate" .)