Crossword Genius

Ungentlemanly type, even worse with a different leader (7)

Ross

I believe the answer is:

dastard

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'leader' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for dastard that I've seen before include "Cowardly fellow" , "despicable fellow!" , "contemptible scaredy-cat" , "Coward" .)

I've seen this clue in The Guardian.
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