Crossword Genius

Tiresome job that's unhealthy (3)

Ross

I believe the answer is:

fag

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'tiresome job' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?

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

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(Other definitions for fag that I've seen before include "Ciggie" , "smoke" , "Tedious chore" , "Boring task" , "He'll do anything you ask" .)

I've seen this clue in The Times.
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