A number one in Abba hit, health hazard! (8)

I believe the answer is:

asbestos

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'health hazard' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'a number one in abba hit' is the wordplay.
'number one' becomes 'best' (I've seen this in another clue).
'in' is an insertion indicator.
'abba hit' becomes 'sos' (SOS was a hit song for ABBA).
'best' inserted within 'sos' is 'sbestos'.
'a'+'sbestos'='ASBESTOS'

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(Other definitions for asbestos that I've seen before include "Fire-retardant material" , "Fire-resistant material dangerous to health" , "we now know to be dangerous" , "Firewall material" , "Boss set a non-burning material up" .)

I've seen this clue in The Times.

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