Moor and lake to west, by border county (7)

I believe the answer is:

leitrim

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'county' is the definition.
(county of Ireland)

'moor and lake to west by border' is the wordplay.
'moor' becomes 'tie'.
'and' says to put letters next to each other.
'lake' becomes 'L' (geographical abbreviation).
'to west' says the letters should be written backwards (the letters are written right to left).
'by border' becomes 'rim' (I've seen this before. I am not sure about the 'by' bit.).
'tie'+'l'='tiel'
'tiel' reversed gives 'leit'.
'leit'+'rim'='LEITRIM'

Can you help me to learn more?

(Other definitions for leitrim that I've seen before include "County of Ireland" , "Could the county rile Tim?" , "Limiter of Irish county" .)

I've seen this clue in The Times.

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