Get part of the story wrong and it’s nonsense! (3)
I believe the answer is:
rot
'it's nonsense' is the definition.
(thesaurus)
'get part of the' is the wordplay.
'get' becomes 'ro' (I am not sure about this - if you are sure you should believe this answer much more).
'part of' says to take the initial letters (I've seen 'part' mean this).
The initial letter of 'the' is 't'.
'ro'+'t'='ROT'
'story wrong and' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for rot that I've seen before include "Corruption" , "crumble" , "SECOND PART OF 25" , "Decay, moulder" , "Informal nonsense" .)