The only reason I saw "chip" for 27d is that the clue is connected to clue 1d to which the answer is "on one's shoulder" (anagram)
If one has a grievance, one has a "chip on one's shoulder" and so if the answer to 1d came after the answer to 27d, this gives "chip" for 27d.
Last one should be easy but......
18A ... American one taking her cut of trick (4) . I have H-A-
Perhaps it links to previous clue : 15A Scrubber turning trick in front of a hospital ..... (6) . This is loofah. Any ideas?