England took the second Ashes Test into a fifth day at Adelaide - but they are still staring down the barrel of a heavy defeat after being set 531 for victory.Joe Root made 87 and Kevin Pietersen 53, the pair putting on a partnership worth 111, England’s best stand of the series so far, as the tourists closed on 247-6.Openers Alastair Cook and Michael Carberry had both been caught at fine-leg early in the day after Australia captain Michael Clarke - perhaps with an unsettled weather forecast in mind - declared his side’s second innings on its overnight position of 132-3.But Root and Pietersen steadied the innings, the latter launching Steve Smith’s leg-spin for three sixes on the way to a 90-ball half-century.However, his downfall came after Clarke brought on his nemesis Peter Siddle, the seamer getting the right-hander to drag an inside edge onto his stumps. It was the second occasion in the match he’d fallen to the seamer and the ninth time in Tests.And worse quickly followed for the tourists when Ian Bell - left stranded on 72 not out in England’s first innings total of 172 - was caught for six by a diving Mitchell Johnson at mid-on from a full toss off Smith.Inside edgeRoot looked on course to register England’s first three-figure score of the series - it was even the first time they had passed 200 as a team - until an inside edge trying to defend Lyon off the back foot resulted in wicketkeeper Brad Haddin taking a reactive catch diving forwards.The Yorkshireman had hit nine boundaries in a 194-ball knock that will surely underpin his place at number three in the order, for the near future at least.When Ben Stokes, who had battled hard to make 28, was caught at slip by Clarke off Ryan Harris, it seemed the door was ajar for Australia to wrap up the match on Sunday.But Matt Prior and Stuart Broad mixed some solid defence with the odd counter-attacking punch to put on an unbroken alliance of 37 for the seventh wicket.Both avoided suffering the ignominy of bagging pairs to get England through to the close, Prior finishing up unbeaten on 31 with Broad 22 not out.Australia’s surprise declaration earlier had denied David Warner (83no) the chance of his second century of the series but maximised the time available for them to pick up the 10 wickets required for victory and a 2-0 lead in the series.The home side made the ideal start to that quest when Johnson - who took 7-40 in the first innings - dismissed Cook for the second time in the match, the England skipper caught hooking for a solitary run.Carberry (14) was undone in similar fashion to his captain, helping a short ball from Siddle to deep backward square-leg, where Lyon took a well-judged catch.Yet unlike at the Gabba, England managed to at least stave off the threat of defeat until the final day. They will now hope a combination of bad weather and brave batting from their tail can see them escape unscathed to Perth.