In some ways, pairing Def Leppard and Poison together doesn’t seem like a good idea. Leppard is a British act associated with the New Wave of British Heavy Metal movement. Poison is an American act that emerged out of the ’80s glam metal scene. But these two bands (they also toured together last summer) do have one thing in common — they know how to please their fans. In front of a half-capacity crowd at Quicken Loans Arena last night, both groups resorted to arena rock clichés (sing-a-longs, hand-slapping, acoustic segments) during their respective sets that, while entertaining, ultimately rang hollow.