Gangster disembowelled musical relative (7)
I believe the answer is:
grannie
'relative' is the definition.
(grannie is a kind of relative)
'gangster disembowelled musical' is the wordplay.
'disembowelled' says to hollow out the word (remove centre letters).
'musical' becomes 'annie' (Annie is a Broadway musical).
'gangster' with its centre taken out is 'gr'.
'gr'+'annie'='GRANNIE'
(Other definitions for grannie that I've seen before include "old lady" , "Older relative" , "senior citizen, perhaps" .)