Hero defies some to break down (5)
I believe the answer is:
erode
'break down' is the definition.
(I've seen this in another clue)
'hero defies some' is the wordplay.
'some' indicates a hidden word.
'ERODE' is hidden within 'hero defies'.
'to' acts as a link.
(Other definitions for erode that I've seen before include "Slowly remove" , "Eat away" , "Gradually wear away" , "Wear away with weather" , "fragment" .)