Well, "slightly" for SUB took me a while to get. But that's just my failing! "Under" seems a little superfluous to me, though.

I think it works as a clue, however.

Thanks - I see your point. But without the preposition, the definition would have been 'ruling' - which could be perceived as a verb, therefore the solution would have ended .......ING. Yes?

The fact it *could* be perceived as a verb is irrelevant. It's OK to be misleading in a cryptic clue! Just because the straight def ends in "ING" doesn't mean the solution necessarily has to do so, as long as it's still a valid definition.

Here's one. Let's see how you go:
Attractive ribbon put to sound use [8,4]