Born in England and raised on football in Geelong, Idun came to the Greater Western Sydney Giants at pick 61 after the club traded up in the 2018 draft. He shared the club's Best Finals Player award in 2023, played every match in 2024 to finish fourth in the Kevin Sheedy Medal, then went one better with third place and the Coaches Award in 2025. He has played 140 AFL games.