Empty manhole opening behind Charlie a long way (10)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Empty manhole opening behind Charlie , a long way M <anhol> E (“empty” means all inside letters are dropped) + GAP (=opening) + ARSE (=behind, derrière) + C (=Charlie, in NATO alphabet); a megaparsec is a huge distance in space, hence “a long way”