Phone Edward – somewhat essential (4)
I believe the answer is:
need
'essential' is the definition.
('need' can be a synonym of 'essential')
'phone edward somewhat' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'NEED' is hidden in the letters of 'phone edward'.
(Other definitions for need that I've seen before include "A condition" , "state requiring relief" , "Call" , "Desideratum" , "Lack or require" .)