A measure used in plainchant (4)

I believe the answer is:

inch

'a measure' is the definition.
(inch is a kind of measure)

'in plainchant' is the wordplay.
'in' indicates the answer is hidden within the clue.
'INCH' is hidden in the letters of 'plainchant'.

'used' is the link.

(Other definitions for inch that I've seen before include "Fraction of a foot" , "2.54 centimetres" , "See 12" , "Advance slowly" , "Islet (Scots); twenty-five.four mm" .)

I've seen this clue in the Evening Standard.

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