Reynard. Replacing grip with the interloper means you’re only changing the first and last letters of grip. Therefore only 36d is affected and it remains a real word. In removing the interloper entirely from its original position you are, again, left with (shorter) real words.
Meanwhile I am struggling on with this beast of a crossword. I still have the NE corner to complete and 3 clashing clues to locate. The missing elements of the 3,5 theme should help... albeit tomorrow morning now with fresh eyes.
Could someone put me out of my misery on the parsing for 34a. I’ve sorted the “taste”, the extra words and the def but can’t really see what “only” has to do with it. My 2003 BRB is struggling!