Tramp, maybe — one omitted from file (6)

I believe the answer is:

dosser

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'tramp' is the definition.
(dosser is a kind of tramp)

I cannot understand how the rest of the clue works.

(Other definitions for dosser that I've seen before include "Idler, layabout" , "Vagrant who lives in cheap lodging house" , "Homeless person" , "One who sleeps rough" , "Idle person" .)

I've seen this clue in The Times.

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