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' indicates the answer is hidden within the clue.
'INCH' can be found hidden inside '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.

Want a hint initially instead of a full solution? Install my app