A musical group to allow charm (6)
I believe the answer is:
amulet
'charm' is the definition.
(I know that amulet is a type of charm)
'a musical group to allow' is the wordplay.
'a musical group' becomes 'amu' (I can't explain this - if you can you should give a lot more credence to this answer).
'to allow' becomes 'let' (synonyms).
'amu'+'let'='AMULET'
Can you help me to learn more?
(Other definitions for amulet that I've seen before include "Thing worn as charm against evil" , "Charm to protect from evil" , "Mascot" , "Charm warding off evil" , "Protective ornament" .)