Flawed heroic figure's end concealed for so long (7)
I believe the answer is:
cheerio
'for so long' is the definition.
(both can mean goodbye)
'flawed heroic figure's end concealed' is the wordplay.
'flawed' indicates anagramming the letters (I've seen this in other clues).
'end' says to take the final letters.
'concealed' is an insertion indicator.
The final letter of 'figure' is 'e'.
'heroic' is an anagram of 'cherio'.
'cherio' enclosing 'e' is 'CHEERIO'.
(Other definitions for cheerio that I've seen before include "An informal hearty goodbye" , "Final message" , "Say this before drinking" , "Bye" , "A hearty farewell, begins with applause" .)