Rationalise holding another Scottish island (4)

I believe the answer is:

iona

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'scottish island' is the definition.
(island of the Hebrides)

'rationalise holding another' is the wordplay.
'IONA' is hidden in amongst the letters.
However, I am unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for iona that I've seen before include "early Christian centre" , "Greek sea god" , "part of Scotland" , "monastic retreat" , "Inner Hebridean island" .)

I've seen this clue in The Irish Times.

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