Vexed expression tour leader used in Bangkok market (4)

I believe the answer is:

baht

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'in bangkok market' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'vexed expression tour leader' is the wordplay.
'vexed expression' becomes 'bah' (I have seen 'Expression of contempt ' mean 'bah' so perhaps 'expression' could also mean 'bah'. I am not sure about the 'vexed' bit.).
'leader' says to take the initial letters.
The initial letter of 'tour' is 't'.
'bah'+'t'='BAHT'

'used' is the link.

Can you help me to learn more?

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

I've seen this clue in The Irish Times.

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