[Inkspot] Thanks for trying - no-one else has. Your answer isn't what I had in mind. It has occurred to me that it's one of those clues that 'could' be several things, therefore, not a very good one! If anyone else wants to have a crack at it, please be my guest. I compiled it myself and deliberately tried to 'crypticize' it, thinking I was being clever. Shall I post some letter clues?
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?