Walker losing one of their rights is still a walker (6)

I believe the answer is:

ambler

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'walker' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for ambler that I've seen before include "toddler?" , "Horse" , "Eric -, English author (The Mask of Dimitrios)" , "Walker who's rather slow" , "Writer called Eric" .)

I've seen this clue in The Telegraph.

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