Italian holiday island company adopting Channel Islands? It’s light-hearted stuff (9)
I believe the answer is:
'light-hearted stuff' is the definition.
(light-hearted or lively piece of music)
'italian holiday island company adopting channel islands?' is the wordplay.
'italian holiday island' becomes 'capri'.
'company' becomes 'co' (abbreviation).
'adopting' is an insertion indicator.
'channel islands?' becomes 'ci'.
'co' going around 'ci' is 'ccio'.
'it's' acts as a link.
(Other definitions for capriccio that I've seen before include "Kind of free composition", "Lively work", "Strauss opera", "Free instrumental composition, played with improvisation", "Lively and free musical piece".)