Compilers from Connaught: their best friends? (5,7)

I believe the answer is:

irish setters

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'best friends?' is the definition.
Although both the answer and definition are plural nouns, I don't understand how they can define each other.

'compilers from connaught their' is the wordplay.
I cannot really see how this works, but
'compilers' could be 'setters' (compilers or setters of cryptic crosswords) and 'setters' is located in the answer.
The remaining letters 'irish' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Telegraph.

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