Calm, primate eating green seeds (7)
I believe the answer is:
appease
'calm' is the definition.
(appeasing is a kind of calming)
'primate eating green seeds' is the wordplay.
'primate' becomes 'ape' (ape is a kind of primate).
'eating' indicates putting letters inside.
'green seeds' becomes 'peas'.
'ape' placed around 'peas' is 'APPEASE'.
(Other definitions for appease that I've seen before include "Quiet" , "Satisfy demands by making concessions" , "Propitiate by concessions" , "Placate (someone) by agreeing to their demands" , "Mollify by making concession" .)