It's said to be high in the Hebrides (4)
I believe the answer is:
skye
'hebrides' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'it's said to be high in the' is the wordplay.
'to be high' says to take the initial letters (I've seen 'highest of' mean this (top letter - down clues only)).
'in the' becomes 'kye' (I can't justify this - if you can you should believe this answer much more).
The first letter of 'said' is 's'.
's'+'kye'='SKYE'
Can you help me to learn more?
(Other definitions for skye that I've seen before include "Island in a boat song about Flora MacDonald and Bonnie Prince Charlie" , "Destination of a princely boat trip" , "Scotland island" , "Scots isle" , "Portree's isle" .)