27 Start off season before umpire returns with drug in hamper (9)
hamper/INTERFERE :  W(first letter,start) taken away(off) from WINTER(season) +(before) reversal(returns) of REF(eree,umpire) +(with) E(Ecstasy drug).  Defn:  To meddle in and thus hamper proceedings.
Guardian Quiptic 599 Pan