Deranged maestros finally turn out medley (10)
I believe the answer is:
assortment
'medley' is the definition.
(I've seen this before)
'deranged maestros finally turn out' is the wordplay.
'deranged' indicates an anagram.
'finally' suggests the final letters.
The final letters of 'turn out' are 'nt'.
'maestros' is an anagram of 'assortme'.
'assortme'+'nt'='ASSORTMENT'
(Other definitions for assortment that I've seen before include "Mixture" , "Miscellany" , "Variety" , "Medley" , "Miscellaneous collection" .)