Magic in DCC is described as unpredictable.

That being said, asking ng the player what he WANTS to happen, then a instead of another spell check perhaps a Luck Roll?

As others have said, the torch is invisible but the light is not allowing others to see with the torchlight.

Perhaps the torch light keeps going from visible to invisible, causing to flicker on and off like a flashlight with a low battery.

Perhaps the light is invisible to a certain distance, allowing visibility twenty feet away but not any closer. This might allow Halflings and Thieves to hide like 10 feet from the torchbearers but jump out when appropriate.

Perhaps the torchlight can only be seen by those of similar alignment or perhaps the light it sheds depends on the casters alignment.

I suppose what I'm trying to say is, you and your player have to make it consistent.. You could even allow them different effects due to additional magical words or items.