Clear leader in variety show (9)
I believe the answer is:
Here is my best explanation:
'clear' is the definition.
'leader in variety show' is the subsidiary indication.
'leader in' says to take the initial letters.
'show' becomes 'indicate' ('indicate' can be a synonym of 'show'**).
The first letter of 'variety' is 'v'.
(Other definitions for vindicate that I've seen before include "Few show", "Avenge or exonerate", "Justify, clear", "Divine cat (anag.)", "Justify by evidence or results", "Successfully defend", "support", "Show to be right or justified", "Justify or exonerate" and "Deflect criticism".)