Prime Minister must accept rubbish start to election for now (3,3)
I believe the answer is:
pro tem
'for now' is the definition.
('pro tem' can be a synonym of 'for now')
'prime minister must accept rubbish start to election' is the wordplay.
'prime minister' becomes 'pm' ('PM' can be a synonym of 'prime minister').
'must accept' is an insertion indicator.
'rubbish' becomes 'rot' (I've seen this before).
'start to' says to take the initial letters.
The initial letter of 'election' is 'e'.
'rot'+'e'='rote'
'pm' placed around 'rote' is 'PRO TEM'.
(Other definitions for pro tem that I've seen before include "until proper arrangement is made" , "For the time being, to the old Romans in short" , "'For the time being (3,3)'" , "For the present" , "For the time being (Latin abbreviation)" .)