Scottish or Irish Gaelic language (4)
I believe the answer is:
erse
I believe this clue is a double definition.
'scottish' is the first definition.
(I've seen this in another clue)
'irish gaelic language' is the second definition.
(I've seen this before)
(Other definitions for erse that I've seen before include "Old Gaelic for the seer" , "Old Scots or Irish Gaelic" , "Name sometimes given to languages of the Celts in Ireland and Scotland" , "Celtic tongue" , "Possibly the language" .)