No, not clean as a whistle. Ambrose can't lose momentum on his road to Lesnar. I highly, highly doubt he'll win. I don't expect him to. But it'd be smart to play into his character they've been going with. Triple H just needs to throw everything at him, but Ambrose won't stay down. Cue the typical 'reff takes small bump and is down for 10 minutes' spot, and Ambrose takes advantage. He hits his finisher, but the reff just won't move. No other reff comes to do the count(could say The Authority threatened them to back off). Dean tries to wake up the reff, and that's were HHH hits him with a low blow. Then spit on him, something. Be such a heel the crowd just despises it. Triple H gets his sledgehammer and beats the crap out of Ambrose, and then finishes him off.
Orr Ambrose is able to take the sledgehammer from Trips, and hits him a couple of times only to be caught by the ref and DQ'd.
Either way Ambrose looks strong in defeat, and the crowd will hate Triple H for destroying their fan favorite. Not saying that it'll shift the crowd at Mania, but it could be a little bit more in Roman's favor. Even if it is 30% of the crowd that cheers him, it'll be an improvement.