The sharp side of the aged generally shows (4)
I believe the answer is:
edge
'the sharp side' is the definition.
(I've seen this in another clue)
'of the aged generally shows' is the wordplay.
'of' indicates the answer is hidden within the clue.
'EDGE' is hidden in the letters of 'aged generally shows'.
(Other definitions for edge that I've seen before include "Line where soething begins or ends" , "Force" , "Excitement; boundary" , "Margin, extremity" , "Verge" .)