Crossword Genius

Prolific singer likely to publicise work by The Killers? (10)

Ross

I believe the answer is:

supergrass

I'm a little stuck... Click here to teach me more about this clue!

'prolific singer likely to publicise work' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'by the killers?' is the wordplay.
I cannot quite understand how this works, but
'by' could be 'per' (I've seen this in another clue) and 'per' is present in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

(Other definitions for supergrass that I've seen before include "Repentant criminal perhaps" , "Very important police informer" , "He does a lot of shopping" , "Large-scale informer" .)

I've seen this clue in The Telegraph.
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