Crossword Genius

One of those doing the numbers for consigliere dismissing e coli (6)

Ross

I believe the answer is:

singer

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'one' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

I don't understand the remainder of the clue.

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(Other definitions for singer that I've seen before include "Coventry car firm" , "Diva perhaps" , "choirboy?" , "Member of a choir" , "Warbler" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).
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