"Once a spell is granted the Cleric can cast it. When a spell is cast
it may be revoked by the deity. A revoked spell is no longer granted
to the Cleric and can not be cast until the Cleric Communes and
asks for it again."
So - - let's ponder this for a second. Clerics have lost heavier armor in DW (it counts as Clumsy for them, but not for Fighters), and frankly items like poultices, bandages, and so on really give Cure Light Wounds a run for its money - bandages in particular restore 4hp, while CLW only heals 1d8 (not all that much more, tbh).
But Clerics get a boost from that line "may be revoked by the deity". Not just a power boost, potentially, but that one small sentence means that the DM has a clear, concrete way to comment on a god's current feelings towards its loyal servant. You can also be weird and mysterious by revoking certain spells but not others.
At the same time, this is a challenging, fiddly bit of decision-making to embark on - - the DM must remember her principles and abide by them very carefully. Be a fan of the PCs. It's possible that a god could be punishing its disciple by revoking spells, but if so, the DM should make that clear in other ways so the player can address it. If the god is instead micromanaging, then hints or clues about the "mission" the god thinks the Cleric is on right now would be useful.
Don't think about what you're trying to do to or for the player with revocation. Think, in the fiction, what the deity is trying to do to the cleric.