Not exactly a shock for one getting behind supporter (5)
I believe the answer is:
chair
'supporter' is the definition.
(I've seen this before)
'not exactly a shock' is the wordplay.
'not exactly' becomes 'c' (short for 'circa').
'a shock' becomes 'hair' (shock can mean a mass of hair).
'c'+'hair'='CHAIR'
'for one getting behind' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for chair that I've seen before include "Professoriate" , "Backed seat for one" , "Windsor, for example" , "conduct" , "Preside over - seat" .)