Dog treated remedially by Ed (3)

I believe the answer is:

cur

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'dog' is the definition.
(both can mean a despicable person)

I don't understand the rest of the clue.

(Other definitions for cur that I've seen before include "Base fellow" , "Worthless or bad-tempered dog" , "Inferior dog or one of mixed breed" , "Vicious dog" , "Aggressive mongrel" .)

I've seen this clue in the Evening Standard.

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