Blue Grotto island (5)
I believe the answer is:
capri
'blue grotto island' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for capri that I've seen before include "Location for holiday" , "Neapolitan isle" , "Old Ford model - Italian island" , "Island off Italy" , "Italian resort island, once home to Gracie Fields" .)