All you need is to be determined (3)
I believe the answer is:
set
This clue is a double definition.
'all' is the first definition.
(thesaurus)
'is to be determined' is the second definition.
('set' can be a synonym of 'determined')
'you need' is the link.
(Other definitions for set that I've seen before include "Mount (precious stone)" , "Mount (gem); scenery" , "Put down the group of games" , "Become solid like jelly" , "Group; unchanging" .)