Most unpleasant people, sneaks (6)

I believe the answer is:

creeps

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'sneaks' is the definition.
('creep' can be a synonym of 'sneak')

I can't explain the remainder of the clue.

(Other definitions for creeps that I've seen before include "Moves slowly - like servile people?" , "treads softly" , "Unpleasantly strange people" , "Crawls silently" , "'''Tomorrow, and tomorrow, and tomorrow, ... in this petty pace from day to day'' (Shakespeare) (6)'" .)

I've seen this clue in the Evening Standard.

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