Terrier — mine’s escaped from Pacific island (5)

I believe the answer is:

cairn

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'terrier' is the definition.
(cairn terrier is a kind of terrier)

I don't understand the rest of the clue.

(Other definitions for cairn that I've seen before include "Mound of stones on mountain top" , "Memorial mound of stones" , "Pile of stones - type of terrier" , "simple grave marker" , "Small terrier" .)

I've seen this clue in The Times.

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