Champions are fed up with objectives (7)
I believe the answer is:
defends
'champions' is the definition.
('defend' can be a synonym of 'champion')
'fed up with objectives' is the wordplay.
'fed up' becomes 'def' ('fed' going up in a down clue).
'with' is a charade indicator (letters next to each other).
'objectives' becomes 'ends' (I've seen this before).
'def'+'ends'='DEFENDS'
'are' is the link.
(Other definitions for defends that I've seen before include "Protects from attack" , "Supports" .)