Ravel’s magical charm in need of piano (8)
I believe the answer is:
entangle
'ravel's' is the definition.
(as opposed to unravel)
'magical charm in need of piano' is the wordplay.
'magical charm' becomes 'pentangle' (magical symbol).
'in need of' indicates named letters should be taken away.
'piano' becomes 'p' (musical abbreviation).
'pentangle' with 'p' removed is 'ENTANGLE'.
(Other definitions for entangle that I've seen before include "Make twisted" , "Involve in complications" , "Entwine or involve in something complicated" , "Involve in complicated circumstances" , "Snare" .)