Some hogwash, so that's flipping nonsense (4)
I believe the answer is:
tosh
'nonsense' is the definition.
(I know that tosh is a type of nonsense)
'some hogwash so that's flipping' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'flipping' says the letters should be written in reverse.
'hsot' is hidden within 'hogwash so thats'.
'hsot' written backwards gives 'TOSH'.
(Other definitions for tosh that I've seen before include "13 [TRIPE]" , "Boloney" , "Pal" , "Humbug" , "Hooey" .)