no, you cannot clear US borders at YYZ for Irish citizens i am sure.
if you are in transit at YYZ which it appears you are, your bags will go thru to CLE, and you just go to transit lounge for your next flight to CLE if you have boarding cards for that sector, if you dont then you go to your airline's transit desk for your cards.
if you are not just in transit YYZ and stay more than xxhours then you must clear Canadian customs and get your bags.
if you were flying LHR-DUB-JFK (DUB in transit) for instance then you can clear US borders at DUB i understand...