Would slipping a small object into an inner pocket count?
This is the kind of thing that Pathfinder relies on the GM and real-world knowledge to handle. Materials have similar opacity as they do in real life.
So does an inner pocket count? That depends on the material it’s made from and the strength of the light. The rules don’t go into enough detail to really specify. Certainly one would expect that with a small light, heavy clothing (to say nothing of actual armor) would be opaque enough, but with a particularly strong light, or lighter material (I mean, have you seen some of the artwork?), light may very well be visible.
Fantastic materials, and some magical effects, do go out of their way to discuss their opacity—usually in the context of “line of sight” and so on. Where available, that is probably useful information for the GM to decide something like this—if you can see through something, by definition light is passing through it, and if you can’t, then that means light isn’t getting through.