Girl originally from a Scottish island? (5)
I believe the answer is:
fiona
'girl' is the definition.
'originally from a scottish island?' is the wordplay.
'originally' says to take the initial letters.
'a scottish island?' becomes 'iona' (I've seen this before**).
The first letter of 'from' is 'f'.
'f'+'iona'='FIONA'
(Other definitions for fiona that I've seen before include "Girl's name, meaning fair in Gaelic" , "Girl" , "Girl's name (not Flora)" .)