The clan is excited about daughter of the northern isles (10)

I believe the answer is:

shetlandic

'of the northern isles' is the definition.
(relating to the Shetland Islands)

'the clan is excited about daughter' is the wordplay.
'excited' indicates anagramming the letters.
'about' is an insertion indicator.
'daughter' becomes 'd' (genealogical abbreviation).
'the'+'clan'+'is'='theclanis'
'theclanis' is an anagram of 'shetlanic'.
'shetlanic' enclosing 'd' is 'SHETLANDIC'.

I've seen this clue in The Times.

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