Don't stand for a fib (3)
I believe the answer is:
lie
I believe this clue is a double definition.
'don't stand' is the first definition.
'for a fib' is the second definition.
(a fib is a lie)
(Other definitions for lie that I've seen before include "Stay hidden" , "situation" , "Assume a horizontal position" , "Tell tales" , "Mistruth" .)