It encapsulates the competition between Trinity and UCD (15)

I believe the answer is:

intercollegiate

I'm a little stuck... Click here to teach me more about this clue!

'it encapsulates the competition' is the definition.
The definition suggests a singular noun but the answer is not.

'between trinity and ucd' is the wordplay.
I cannot quite see how this works, but
'between' could be 'inter' and 'inter' is found in the answer.
The remaining letters 'collegiate' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Irish Times.

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