Closely analyse practice by county GAA team (5,4)

I believe the answer is:

drill down

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'closely analyse' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'practice by county gaa team' is the wordplay.
I cannot quite see how this works, but
'practice' could be 'drill' (synonyms) and 'drill' is present in the answer.
'county' could be 'down' (County Down in Northern Ireland) and 'down' is found within the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Irish Times.

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