Lady-killer, heroic, as an ovation shows (8)
I believe the answer is:
casanova
'lady-killer' is the definition.
(I've seen this before)
'heroic as an ovation shows' is the wordplay.
'shows' indicates the answer is hidden within the clue.
'CASANOVA' is hidden in the letters of 'heroic as an ovation'.
(Other definitions for casanova that I've seen before include "Rake" , "Notorious lover" , "Predatory male" , "Memoirist" , "18th century Italian lover" .)