Necessary for Thai bantamweight to lose eight in a row (4)

I believe the answer is:

baht

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'necessary for thai' is the definition.
I know that 'thai' relates to this answer. I also know that both the answer and definition are singular nouns

I can't explain the rest of the clue.

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(Other definitions for baht that I've seen before include "Asian money" , "Tin" , "18 across currency" , "Thai money" , "In Thailand ready" .)

I've seen this clue in The Telegraph.

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