Boss's ruse, mere playing around (8)
I believe the answer is:
employer
'boss's' is the definition.
(thesaurus)
'ruse mere playing around' is the wordplay.
'ruse' becomes 'ploy' (I've seen this before).
'playing' is an anagram indicator.
'around' indicates putting letters inside.
'mere' is an anagram of 'emer'.
'ploy' inserted within 'emer' is 'EMPLOYER'.
(Other definitions for employer that I've seen before include "Boss or proprietor" , "One engaging staff" , "One for whom people work" , "One paying staff" , "One's worked for" .)