Need to change prime minister (4)

I believe the answer is:

eden

'prime minister' is the definition.
(Anthony Eden, UK PM 1955-57)

'need to change' is the wordplay.
'to change' indicates anagramming the letters.
'need' with letters rearranged gives 'EDEN'.

(Other definitions for eden that I've seen before include "Biblical garden" , "The first habitat" , "The most enchanting garden of all" , "The best of all gardens" , "Paradise - ex-PM" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.