Champion finds partner online? (7)
I believe the answer is:
espouse
'champion' is the definition.
(both can mean to endorse or agree with)
'partner online?' is the wordplay.
I cannot quite see how this works, but
'partner' could be 'spouse' (synonyms) and 'spouse' is found in the answer.
'online?' could be 'e' (as in e-mail or e-commerce) and 'e' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'finds' is the link.
(Other definitions for espouse that I've seen before include "Marry -- take on as a cause" , "See opus (anag)" , "Give support to - see soup (anag)" , "Give support to, say a cause" , "Adopt - give support to" .)