Old soldier on island line (9)

I believe the answer is:

legionary

'old soldier' is the definition.

'on island line' is the wordplay.
'on' becomes 'leg' (cricket term, fielding positions).
'island' becomes 'iona' (I've seen this before).
'line' becomes 'ry' (abbreviation for railway).
'leg'+'iona'+'ry'='LEGIONARY'

(Another definition for legionary that I've seen is " soldier".)

I've seen this clue in The Times.

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