Steal the show winning leg (7)
I believe the answer is:
upstage
'steal the show' is the definition.
(I've seen this in another clue)
'winning leg' is the wordplay.
'winning' becomes 'up' (I've seen this in other clues).
'leg' becomes 'stage' (synonyms).
'up'+'stage'='UPSTAGE'
(Other definitions for upstage that I've seen before include "Divert attention from another as actor might in play" , "Stand-offish (sl.)" , "Divert attention from another as actor may" , "Be haughty towards" , "dwarf?" .)