Lies, untruths (4)
I believe the answer is:
fibs
This clue is a double definition.
'lies' is the first definition.
(I know this)
'untruths' is the second definition.
(fib is a kind of untruth)
(Other definitions for fibs that I've seen before include "Trivial lies as by child" , "Harmless little lies" , "Little white lies" .)