Diana's musical show to unsettle? (10)
I believe the answer is:
disconcert
'unsettle?' is the definition.
(unsettling is a kind of disconcerting)
'diana's musical show' is the wordplay.
'diana's' becomes 'Di's' (Di is short for Diana).
'musical show' becomes 'concert' ().
'dis'+'concert'='DISCONCERT'
'to' is the link.
(Other definitions for disconcert that I've seen before include "Throw" , "upset" , "Dismay" , "Bother" , "Disturb, unsettle" .)