You would have to be low health for the undressing animation to play. (Same thing applies to the mobs.)
Just get hit with the normal attacks and not the grabs where hearts pop up.
Stripping occurs when either you, the enemy, or both are at or below half HP I believe. However, the animation for being stripped was removed in v0.0.8 since the dev figured it'd probably be a waste of time to create animations for the player getting stripped by each individual enemy, and each individual enemy stripping themselves (assuming they have clothes to strip).
The undressing animations were dropped with either version 0.0.4 or 0.0.5 so go back in this thread and try either one of those.
It's still in in 0.0.6, I don't believe there was any 0.0.7 or if there was it wasn't shared here (so far as I know), and in v0.0.8 it was removed. Please correct me if I'm wrong though.
I think he is talking about the version where they have an animation of them striping you and not just having your clothes fly off. If that's still in the game, then I have no clue how to get that to work.
As spacefish said, the animations were removed and now your clothes simply fly off. So unfortunately no, there is no way to trigger the animation anymore, at least that I'm aware of.