Unknown online supporter of African native (5)
I believe the answer is:
zebra
'african native' is the definition.
(I know that zebra are native to Africa)
'unknown online supporter' is the wordplay.
'unknown' becomes 'z' (algebra).
'online' becomes 'e' (as in e-mail or e-commerce).
'supporter' becomes 'bra' (a bra gives support to breasts).
'z'+'e'+'bra'='ZEBRA'
'of' is the link.
(Other definitions for zebra that I've seen before include "Striped quadruped" , "Kind of crossing?" , "that's stripy" , "Black and white striped animal" , "Striped horse-like animal" .)