http://www.mcall.com/ Def Leppard roars into fair a.. Crowd 'gets rocked' by '80s hits of an older, wiser pop-metal band. 09/01/99 Loud, thumping drumbeats. Smoke on stage and off. Big hair, tight jeans and the once-popular two-fingered salute to heavy metal.With Def Leppard on the grandstand stage, the 1980s were back at the Allentown Fair on Tuesday night -- in one big, loud and hairy way. With the energy it once displayed in music videos, Def Leppard pounded, screeched and guitar-roared its way through hits that made the pop-metal band one of the most successful rock acts in history. But the teen-agers who wore skimpy outfits and skull-and-crossbone rings and listened to the music a decade ago are in their 30s, cutting their hair to fit the grunge look. Even the band has toned down its act, no longer wearing the British Union Jack shirts that were once its signature. The members are a little older and probably a lot wiser these days, having lost guitarist Steve Clark, who died of a drug and alcohol overdose. Rick Allen, the drummer, lost his left arm in a car accident. And the band's star has fallen . It's no longer as popular as it was before grunge, rap and hip-hop began to dominate the music scene in the 1990s. But as Def Leppard sang during the hour-and-a-half show, Tuesday night was a time to ''get rocked.'' So multimillion selling albums, MTV and past glory were not so important. When the audience heard the opening guitar chords of ''Rock Rock (Till You Drop),''from the band's breakthrough ''Pyromania'' album, lighters popped open, and many of the 8,555 people thrust their hands in the air, gesturing the two-fingered heavy metal salute. ''Allllentown!'' shouted lead singer Joe Elliot, one of two members who have been with the band since its start 20 years ago. ''We are Def Leppard, and this is what we do!'' Two muscular men in their 30s danced to the band's pounding, menacing ''Women'' from the band's most successful album, ''Hysteria.''. Others high-fived when they heard the opening electric strings of ''Too Late for Love,''again from ''Pyromania.'' Women jumped on their boyfriends' shoulders as the band performed music from its latest CD, ''Euphoria,'' released earlier this year. Elliot's voice was hoarse, but he forced his trademark screeches, mustering enough energy to shout ''C'mon Allentown'' as often as he could. And every time he did, more hands and lighters shot up. Moon Dog Mane opened for Def Leppard. Tom Davis