Turn a key by mistake (5)

I believe the answer is:

gooff

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'turn a' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'key by mistake' is the wordplay.
'key' becomes 'f' (musical key).
'by' says to put letters next to each other.
'mistake' becomes 'goof' (I've seen this before).
'f' put after 'goof' is 'GOOFF'.

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I've seen this clue in The Daily Express.

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