Language from Merseyside? (4)
I believe the answer is:
erse
'language' is the definition.
(historical term for Scottish Gaelic)
'from merseyside?' is the wordplay.
'from' says the answer is hidden in the clue.
'ERSE' is hidden within 'merseyside'.
(Other definitions for erse that I've seen before include "Kind of Gaelic for seer" , "Old Celtic language" , "Possibly the language" , "Old name for Celtic languages" , "Old Gaelic for the seer" .)