Throughout the 2021 Under-19s season, Bennison made eight appearances, scoring seven tries across the campaign.
On 17 September 2021, Bennison made his professional debut, scoring a try in St Helens' 26–14 loss to Salford.[3]
On 24 September 2022, Bennison scored a try during St Helens 2022 Super League Grand Final victory over Leeds.[4]
Bennison played 19 games for St Helens in the 2023 Super League season as the club finished third on the table. Bennison played in St Helens narrow loss against the Catalans Dragons in the semi-final which ended St Helens four-year dominance of the competition.[5]
Bennison played 15 matches for St Helens in the 2024 Super League season as the club finished sixth on the table. He played in St Helens golden point extra-time playoff loss against Warrington.[6]