Boy king reversed it, employing all the players (5)
I believe the answer is:
tutti
'all the players' is the definition.
(I've seen this before)
'boy king reversed it' is the wordplay.
'boy king' becomes 'tut' (I've seen this in another clue).
'reversed' shows that the letters should be reversed in order.
'it' reversed gives 'ti'.
'tut'+'ti'='TUTTI'
'employing' is the link.
(Other definitions for tutti that I've seen before include "- - -frutti" , "With all instruments twenty four Acdn (music)" , "Section for all musicians" , "Every instrument to play" , "All (musical players)" .)