Flank dies away (4)
I believe the answer is:
side
'flank' is the definition.
(I've seen this in another clue)
'dies away' is the wordplay.
'away' is an anagram indicator (letters move away from their original places).
'dies' with letters rearranged gives 'SIDE'.
(Other definitions for side that I've seen before include "Ides (anag.)" , "Accompanying" , "Left or right, say" , "Edge - aspect - team" , "long forgotten" .)