Fussy bastard's content: flipping hell! (5)
I believe the answer is:
abyss
'hell' is the definition.
(I know that hell can be written as abyss)
'fussy bastard's content flipping' is the wordplay.
'content' indicates the answer is hidden within the clue (letters contained within the clue).
'flipping' says the letters should be written in reverse.
'ssyba' is hidden in the letters of 'fussy bastards'.
'ssyba' backwards is 'ABYSS'.
(Other definitions for abyss that I've seen before include "Fathomless pit" , "Very large and deep chasm" , "depths of sea" , "something rather deep" , "Deep pit" .)