Oh, yes. Loki is enjoying this. Immensely. He does keep the key teasingly out of reach to the point it looks like he'll just keep pulling it up out of his reach. He could do that, but he doesn't. Instead, when it's obvious Clint is at his limit, he let's the key and consequently his fingers slip into Clint's mouth.

He still looks amused but his attention is completely on his mouth. He keeps a tight grip of the key so he will either have to bite him or work his tongue between his fingers to get it.