If you play Defiance and choose the token, Defiance creates a lasting effect that ignores the effects of the chosen symbol during that test, so when the token is revealed, its effect doesn't get to resolve, because it is entirely ignored by Defiance.

Automatic Success/Failure: Some card effects make an investigator automatically succeed or automatically fail a skill test. If this occurs, depending on the timing of such an effect, certain steps of the skill test may be skipped in their entirety.

• If it is known that an investigator automatically succeeds or fails at a skill test before Step 3 (“Reveal Chaos Token”) occurs, that step is skipped, along with Step 4. No chaos token(s) are revealed from the chaos bag, and the investigator immediately moves to Step 5. All other steps of the skill test resolve as normal.
• If a chaos token effect causes an investigator to automatically succeed or fail at a skill test, continue with Steps 3 and 4, as normal. - FAQ, v.1.7, March 2020

Q: I had a question regarding effects that "cancel all effects of cards committed to this skill test" which arise in both Where Doom Awaits and Sanguine Shadows. Specifically are there any skill effects not cancelled by these effects? My primary confusion results from cards like On the Mend. If On The Mend's Forced effect is also cancelled is it discarded instead of being returned to Vincent's set aside area? If so and Vincent shuffles his discard into his deck how should the Limit 1 in hand be resolved if he attempts to draw a copy of On the Mend when one is already there? Similarly for things like Unrelenting, is the text that returns the sealed tokens at test end canceled? Does it matter because the default rules for seal would resolve at that time? A: We reviewed the scenario cards in question and we will plan to address them in the next FAQ, either with errata or with additional clarification. We believe that, when a scenario card such as Where Doom Awaits states to “cancel the effects and icons” of committed skill cards, this only applies to non-weakness skill cards and only lasts until Step 7 of that skill test. This should clarify our intentions for such a scenario. This should allow for On the Mend to be returned to hand as intended instead of discarded, and for Weakness skill cards such as Dreams of the Deep to function as intended. As for Unrelenting, there is already a rule in place that if a card with sealed tokens leaves play, those tokens are immediately released, so the tokens would still be returned even if the card’s effects were canceled during the test.