A measure used in plainchant (4)

I believe the answer is:

inch

'a measure' is the definition.
(inch is a unit of length)

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

'used' acts as a 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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