Five show support (9)
I believe the answer is:
vindicate
'support' is the definition.
(I've seen this before)
'five show' is the wordplay.
'five' becomes 'v' (roman numeral).
'show' becomes 'indicate' ('indicate' can be a synonym of 'show'**).
'v'+'indicate'='VINDICATE'
(Other definitions for vindicate that I've seen before include "Divine cat (anag.)" , "Successfully defend" , "support" , "Justify or exonerate" , "Justify, clear" .)