Recklessness in musicians playing (7)
I believe the answer is:
abandon
'recklessness' is the definition.
(I've seen this before)
'musicians playing' is the wordplay.
'musicians' becomes 'a band' (a musical group).
'playing' becomes 'on' (on can mean playing or performing).
'aband'+'on'='ABANDON'
'in' acts as a link.
(Other definitions for abandon that I've seen before include "Lack of constraint" , "Junk" , "Leave in the lurch" , "scrap" , "Desert; lack of restraint" .)