Don't stand for untruth (3)
I believe the answer is:
lie
I believe this clue is a double definition.
'don't stand' is the first definition.
'untruth' is the second definition.
(I know that lie is a type of untruth)
'for' is the link.
(Other definitions for lie that I've seen before include "Commit perjury" , "Porky" , "buried" , "A white one is considered harmless" , "found" .)