Doesn't tell the truth (4)
I believe the answer is:
lies
'doesn't tell the truth' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lies that I've seen before include "Perversions of the truth" , "Assumes a horizontal position" , "Reclines" , "Terminological inexactitudes" , "Untruths" .)