This PM no longer has to accommodate English (5)
I believe the answer is:
heath
'this pm' is the definition.
(prime minister Edward Heath)
'no longer has to accommodate english' is the wordplay.
'no longer has' becomes 'hath' (archaic version of 'has').
'to accommodate' is an insertion indicator.
'english' becomes 'E' (abbreviation as in OED).
'hath' going around 'e' is 'HEATH'.
(Other definitions for heath that I've seen before include "Ted - - (former PM)" , "Open land with acid soil" , "Sir Edward - , PM" , "part of Hampstead" , "Area of common unproductive land" .)