Unattached girl's holiday island (8)
I believe the answer is:
discrete
'unattached' is the definition.
(I've seen this before)
'girl's holiday island' is the wordplay.
I cannot really see how this works, but
'girl's' could be 'dis' (Di is short for Diana) and 'dis' is found within the answer.
'island' could be 'crete' (Greek island) and 'crete' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for discrete that I've seen before include "Secret ID (anag) - separate" , "Separated" , "Individually distinct, discontinuous" , "Individual" , "Unattached" .)