The poll finds Democratic frontrunner Hillary Clinton ahead of Trump by just 6 points, a dramatic tightening since July. Trump is the one of three Republican candidates who have been matched against Clinton multiple times in CNN/ORC polling to significantly whittle the gap between himself and the Democratic frontrunner. He trailed Clinton by 16 points in a July poll, and narrowed that gap by boosting his standing among Republicans and Republican-leaning independents (from 67% support in July to 79% now), men (from 46% in July to 53% now) and white voters (from 50% to 55%).
The general election is in over a year. Things are bound to change (and that's IF Trump + Clinton get the nomination). Besides, the Democrats still have the bigger advantage on the electoral college - they can afford to lose some states.