Singer Capital Markets has upgraded online-only fashion retailer ASOS from fair value to buy following the stock's recent weak performance.The broker notes that the shares have fallen by around 40% from the recent June high of 2,468p."However, disruptive factors should be behind them now, and with strong growth expected in overseas markets, and self-help around margin, short term forecasts look achievable and long term sensitivities are unchanged," Singer said.However, the target price is cut from 2,290p to 2,000p.Shares were trading 3.15% lower at 1,475p by 13:53 on Monday.BC