Narrow sun rail (7)

I believe the answer is:

insular

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'narrow' is the definition.
(I've seen this in another clue)

'sun rail' is the wordplay.
'sun rail' can be anagrammed to 'INSULAR'.
Though, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for insular that I've seen before include "Detached - urinals (anag)" , "Narrowly restricted in outlook or scope" , "Detached from mainstream" , "Run sail (anag.)" , "Man, for one, is so" .)

I've seen this clue in The Irish News.

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