Couple of things, first, "enchant" ability shouldn't say target. Second, the problem with having the card be worded this way is that once that creature is no longer attacking, it's no longer a legal enchant target for the Aura so the Aura will drop off.

You want to do something more akin to Dream Leash / Enthralling Hold.

Flash
Enchant creature
You can't choose a creature that isn't attacking as this spell's target as you cast it.
Enchanted creature doesn't untap during its controller's untap step.

In any case, that means it's going to read out a bit glunkily (double negatives are nasty) as well as be wordy, so it will prolly end up being a better fit for uncommon rarity overall.

You; uh; didn't make the horrific wording change that was the impetus for raising this to uncommon.

It's a shame Magic makes it so difficult to express some ideas. "That attacking creature? Give it paralyze" seems like a perfectly simple idea.

yeah sorry haven't gotten around to actually fixing this card yet, I just noticed it didn't have a rarity at all and that was like a 2-second fix. I'll get around to this.