Yield partly once determined (4)
I believe the answer is:
cede
'yield' is the definition.
('cede' can be a synonym of 'yield')
'partly once determined' is the wordplay.
'partly' indicates a hidden word.
'CEDE' can be found hidden inside 'once determined'.
(Other definitions for cede that I've seen before include "Give up (territory)" , "Give up one's rights" , "Give up (power to another)" , "Give up (eg, power)" , "Deliver" .)