Unimportant person’s problem encountered in solving murder? (6)
I believe the answer is:
nobody
'unimportant person's' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
(Other definitions for nobody that I've seen before include "who can square the circle?" , "problem for Morse?" , "being without value" , "Lightweight" , "Literary diarist" .)