Unencumbered by clobber, move fast (6)

I believe the answer is:

streak

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'move fast' is the definition.
'streak' can be an answer for 'move' (streaking is a kind of moving). I am not sure about the 'fast' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for streak that I've seen before include "run out of gear" , "Run naked; long mark" , "Run naked as stunt" , "Move very quickly" , "Band of colour - run naked" .)

I've seen this clue in the Evening Standard.

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