Somehow depend on keeping agreement essentially indeterminate (4-5)
I believe the answer is:
open-ended
'indeterminate' is the definition.
(similar in meaning)
'somehow depend on keeping agreement essentially' is the wordplay.
'somehow' indicates an anagram.
'keeping' means one lot of letters goes inside another.
'agreement' becomes 'yes' (saying yes to something).
'essentially' says to take the centre.
The middle letter of 'yes' is 'e'.
'depend'+'on'='dependon'
'dependon' anagrammed gives 'opnended'.
'opnended' enclosing 'e' is 'OPEN-ENDED'.
(Other definitions for open-ended that I've seen before include "Having no predetermined limit" , "Without fixed limits or restrictions" , "Allowing free debate with no set time to finish." , "With no fixed limit, not circumscribed" , "Having no fixed limit, perhaps a discussion" .)