Earnings disappointed, but looking under the hood, the sell-off could be an opportunity.Shares of steelmaker Cleveland-Cliffs (CLF -9.83%) were falling hard in Tuesday trading, down 9.7% as of 2:10 p.m. ET.Investors apparently took exception with Cliffs missing on revenues and earnings per share in its first-quarter results, which were reported last night. However, the miss appears to be due to an unusual issue with one of Cliffs' customer segments, which appears to have been resolved at the end of the quar ...