Musical works being aspiration of Cockney artist’s (6)
I believe the answer is:
operas
'musical works' is the definition.
(I've seen this before)
'aspiration of cockney artist's' is the wordplay.
'aspiration of cockney' becomes 'ope' (Cockney pronunciation of 'hope').
'artist's' becomes 'RA's' (Royal Academician, member of Royal Academy of Arts).
'ope'+'ras'='OPERAS'
'being' acts as a link.
(Other definitions for operas that I've seen before include "Cos? fan tutte and The Magic Flute" , "Musical dramas" , "Stage dramas" , "Musical shows of Pesaro" , "La Traviata, Aida" .)