The smallest whole number (3)

I believe the answer is:

one

'the smallest whole number' is the definition.
(I've seen this before)

This is the entire clue.

(Other definitions for one that I've seen before include "Single, unitary" , "Leading cardinal" , "Lowest cardinal number" , "both halves" , "Unit" .)

I've seen this clue in The Irish Times.

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