Hotel by peninsula bordering Northern Ireland (8)
I believe the answer is:
hibernia
'ireland' is the definition.
(synonyms)
'hotel by peninsula bordering northern' is the wordplay.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'by' is a charade indicator (letters next to each other).
'peninsula' becomes 'Iberia' (peninsula including Spain and Portugal).
'bordering' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'iberia' enclosing 'n' is 'ibernia'.
'h'+'ibernia'='HIBERNIA'
(Other definitions for hibernia that I've seen before include "Ancient Ireland" , "Old or poetic name for Ireland (8)." , "land once" , "Poetic name for Ireland, now archaic" , "Latin name for Ireland" .)