Hero may see nothing left after one day (4)
I believe the answer is:
idol
'hero' is the definition.
(I've seen this before)
'nothing left after one day' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'left' becomes 'l' (common abbreviation).
'after' means one lot of letters go next to another.
'one' becomes 'I' (Roman numeral).
'day' becomes 'd' (abbreviation for day).
'o'+'l'='ol'
'i'+'d'='id'
'ol' after 'id' is 'IDOL'.
'may see' acts as a link.
(Other definitions for idol that I've seen before include "Who's greatly respected" , "Worshipped figure (not painting); revered person" , "Object of excessive love or devotion" , "Graven image or greatly admired person" , "Someone much loved" .)