Spanner used by motorists (4,6)

I believe the answer is:

road bridge

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'motorists' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'spanner used by' is the wordplay.
'spanner' becomes 'bridge' (I've seen this before).
'used' becomes 'road' (I am not sure about this - if you are sure you should believe this answer much more).
'by' says to put letters next to each other.
'bridge' put after 'road' is 'ROAD BRIDGE'.

Can you help me to learn more?

I've seen this clue in The Guardian, The Globe and Mail and The Telegraph.

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