Untidy teetotaller in Scots river (5)

I believe the answer is:

tatty

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'untidy' is the definition.
(I've seen this before)

'teetotaller in scots river' is the wordplay.
'teetotaller' becomes 'tt' (abbreviation).
'in' means one lot of letters goes inside another.
'scots river' becomes 'tay' (Scottish river. I am not sure about the 'scots' bit.).
'tt' going into 'tay' is 'TATTY'.

Can you help me to learn more?

(Other definitions for tatty that I've seen before include "Worn, scruffy" , "Inferior, scruffy" , "Showing signs of wear and tear" , "Tawdry" , "Worn, shabby (colloq.)" .)

I've seen this clue in The Sun.

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