Resolve both Clever Conjurer abilities, untapping Halo Fountain and the mana-producing permanent.
Activate Halo Fountain's first ability by paying , tapping it and untapping Clever Conjurer, creating a 1/1 Citizen creature token.
Repeat.
This clever loop transforms an ordinary mana source into an unstoppable assembly line by harnessing the hardware of Illusionist's Bracers equipped to Clever Conjurer. When Clever Conjurer taps to untap Halo Fountain, the Bracers spring into action to copy the ability and simultaneously free up your mana-producing permanent for reuse. This lets you repeatedly activate Halo Fountain to pay the white mana, tap it, and untap Clever Conjurer, churning out an endless horde of 1/1 Citizen creature tokens and triggering any entry effects you desire.