A mobility aid (3)

I believe the answer is:

tow

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'a mobility aid' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I can't see?

This is all the clue.

Can you help me to learn more?

(Other definitions for tow that I've seen before include "Drag along behind, say barge" , "form of flax" , "Pull using cable" , "Pull along behind, say barge" , "Prepared fibres" .)

I've seen this clue in the Evening Standard.

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