Top answer with Times supporting exercise (4)
I believe the answer is:
apex
'top' is the definition.
(apex is a top or peak)
'answer with times supporting exercise' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'with' means one lot of letters go next to another.
'times' becomes 'x' (x resembles the multiplication or times sign).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'exercise' becomes 'pe' (Physical Education).
'x' put after 'pe' is 'pex'.
'a' next to 'pex' is 'APEX'.
(Other definitions for apex that I've seen before include "Point or summit" , "The highest point of something" , "The highest point or peak" , "Cheap fare" , "Peak, vertex" .)