Terrence tensed as soon as the other man tried to come between them, his grin fading and his eyes narrowing. More than likely the man was just interfering because he wanted to dance with one of them - with him, apparently - but he was tense, ready to throw a punch or reach for a knife. He couldn't just draw his wand here, in a crowd of Muggles, but he was hardly unarmed against them. Fighting was his thing.
That was not how this was going to be solved, however. The whole thing was pointless, really, because he had absolutely zero interest in the bloke who apparently wanted him pretty badly, nor was it Z's place to protect him, not from pushy blokes in a club or from anyone.
Before he could say anything, though, Z's lips were on his, and then he was left standing there while the two of them took the floor. Well, he thought a bit dazedly, taking in the looks from the other people around them without really paying much attention to them, if Z wanted to amuse himself with this game, fine. After all, it was a win-win situation for him; surely he knew that he was the only one in the club who had any claim on Terrence at all. The only one who could actually snog him, however briefly, and get away with it.
It was hardly a friendly game, though. The other man thought he had a lot to gain and nothing to lose, and Terrence didn't particularly like the way he was looking at Z as though he was an obstacle to be taken out. He glanced around at the onlookers, keeping Z's opponent in the corner of his eye, and tried to gauge what their reaction would be if this turned into a fight. One of Terrence's hands was on his other wrist, in a relaxed hold, but ready to take the knife that was hidden there. If the man showed any inclination towards trying to get Z out of his way in a less friendly manner than dancing, Terrence was ready to move quickly, sink the blade into the man's ribs, and grab Z to Apparate them out of there.
He just hoped that wouldn't be necessary. They wouldn't be able to come back here, at least not without a disguise, after causing a disturbance like that. That would be a shame; Terrence had been enjoying himself.