Intermingling to begin with, Ted Heath and Baker stop fighting (4,3,7)
I believe the answer is:
bury the hatchet
'stop fighting' is the definition.
(to bury the hatchet is to cease hostilities)
'intermingling to begin with ted heath and baker' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'heath' is 'theha' which is located in the answer.
This explanation may well be incorrect...
(Other definitions for bury the hatchet that I've seen before include "Settle quarrel" , "end feud - with 18d" , "sinking of cutter" , "having decided against axing?" , "Become reconciled" .)