Top ten is beneath parody (4)
I believe the answer is:
apex
'top' is the definition.
(I've seen this before)
'ten is beneath parody' is the wordplay.
'ten' becomes 'x' (roman numeral).
'is beneath' is a charade indicator (letters next to each other) (in a down clue).
'parody' becomes 'ape'.
'x' after 'ape' is 'APEX'.
(Other definitions for apex that I've seen before include "The highest point of something" , "Point or summit" , "high-point" , "The tip or highest point (4)" , "crown" .)