Island centre of missionaries (4)

I believe the answer is:

iona

'island' is the definition.
(I've seen this before)

'centre of missionaries' is the wordplay.
'centre of' means to look at the middle letters.
The central letters of 'missionaries' are 'IONA'.

(Other definitions for iona that I've seen before include "Island west of Mull" , "Hebridean location" , "Hebridean island associated with St Columba" , "Site of St Columba's monastery" , "Inner Hebridean island" .)

I've seen this clue in The Telegraph.

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