Support provided by defender (4)
I believe the answer is:
back
This clue is a triple definition!
'support' is the first definition.
(back is a kind of support)
'provided' acts as a link.
'by' is the second definition.
(thesaurus)
'defender' is the third definition.
(I've seen this before)
(Other definitions for back that I've seen before include "Rear -- endorse" , "Support a play - player" , "ago" , "Place where secret deals are done" , "Support; in return" .)