Calm, primate eating nutritious seeds (7)
I believe the answer is:
appease
'calm' is the definition.
(appeasing is a kind of calming)
'primate eating nutritious seeds' is the wordplay.
'primate' becomes 'ape' (large primate).
'eating' means one lot of letters goes inside another.
'nutritious seeds' becomes 'peas'.
'ape' going around 'peas' is 'APPEASE'.
(Other definitions for appease that I've seen before include "Placate (someone) by agreeing to their demands" , "Satisfy demands by making concessions" , "Propitiate by concessions" , "Make peace with" , "Pacify with concessions" .)