Maybe virtuous but losing out to a bad influence (5)

I believe the answer is:

virus

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

'influence' is the definition.
(I have seen 'Corrupting influence' mean 'virus' so perhaps 'influence' could also mean 'virus')

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for virus that I've seen before include "Organism causing disease, or malicious program in computer" , "Cause of computer malfunctions?" , "Hidden destructive code in a computer program, or cause of illness" , "Illegal program introduced maliciously into computers to disrupt them" , "Ultramicroscopic infectious agent" .)

I've seen this clue in The Globe and Mail.

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