A "whole" thing (7)
I believe the answer is:
shebang
'a whole thing' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for shebang that I've seen before include "The whole ___ (entirely)" , "affair in America" , "circumstances" , "(Whole) kit and caboodle" , "The whole thing?" .)