Club singer to cast after bum note (7)
I believe the answer is:
arsenal
'club' is the definition.
(I've seen this before)
'singer to cast after bum note' is the wordplay.
I cannot quite see how this works, but
'bum' could be 'arse' (synonyms) and 'arse' is found within the answer.
'note' could be 'n' (abbreviation) and 'n' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for arsenal that I've seen before include "Mil. magazine; FA club" , "Premier League side founded by munitions workers in 1886" , "array of weapons" , "Munitions store and English football team" , "Store of weaponry" .)