Rapid slides on islands — go sliding (9)
I believe the answer is:
glissando
'rapid slides on islands go sliding' is the definition.
I can't tell whether this definition defines the answer.
'on islands go sliding' is the wordplay.
'on' is an insertion indicator (as in clothing 'on' a person).
'go' indicates an anagram (I've seen 'went' mean this ('go' can mean move)).
'sliding' becomes 'go' (I can't explain this - if you can you should give a lot more credence to this answer).
'islands' anagrammed gives 'lissand'.
'lissand' inserted inside 'go' is 'GLISSANDO'.
Can you help me to learn more?
(Other definitions for glissando that I've seen before include "Effect produced by playing a series of notes very rapidly" , "note series rapidly executed" , "Note with sliding pitch" , "Musical flourish" , "Sliding effect in moving from one musical note to another" .)