Clean up in Beatles' style? (3)

I believe the answer is:

mop

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'clean up' is the definition.
(I've seen this in another clue)

I don't understand how the rest of the clue works.

(Other definitions for mop that I've seen before include "Clean; mass of hair" , "Bundle of soft material at end of stick for cleaning" , "Instrument for cleaning" , "Hair, unkempt" , "Tangle of hair" .)

I've seen this clue in the Evening Standard.

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