Stray from the proper route (3)

I believe the answer is:

err

'stray' is the definition.
(to err is to stray or go wrong)

'from the proper route' is the wordplay.
'from' indicates the answer is hidden within the clue.
'ERR' is hidden in the letters of 'proper route'.

(Other definitions for err that I've seen before include "Go wrong" , "Drop a clanger" , "Bungle" , "do something you shouldn't" , "Boob" .)

I've seen this clue in the Evening Standard, The Globe and Mail and The Irish News.

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