Fingal’s Cave island (6)
I believe the answer is:
staffa
'fingal's cave island' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for staffa that I've seen before include "Hebridean isle" , "Hebridean island: site of Fingal's Cave" , "Fingal's Cave location" , "Island west of Mull" , "Inch" .)