Unable to move quickly (4)

I believe the answer is:

fast

I believe this clue is a double definition.

'unable to move' is the first definition.
(I've seen this before)

'quickly' is the second definition.
(synonyms)

(Other definitions for fast that I've seen before include "Brisk" , "Don't scoff" , "requiring only brief exposure" , "Go without food" , "Can't move" .)

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

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