Get on well (3,2,3)
I believe the answer is:
hit it off
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">get on well</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for hit it off that I've seen before include "Click with someone" , "Agree - get on well together" , "Be well suited" , "Get on well with - or knock from position?" , "Develop a good friendly relationship" .)