Blatantly untruthful woman! (4)
I believe the answer is:
lisa
'blatantly untruthful woman' is the definition.
'Lisa' can be an answer for 'woman'. I am not sure about the 'blatantly untruthful' bit.
'untruthful woman' is the wordplay.
'untruthful' becomes 'l' (I can't explain this - if you can you should believe this answer much more).
'woman' becomes 'Isa'.
'l'+'isa'='LISA'
Can you help me to learn more?
(Other definitions for lisa that I've seen before include "Girl" , "Mona . . . ., famous painting by Leonardo da Vinci" , "Leonardo da Vinci painted the 'Mona ....'" , "Most intelligent of Marge Simpson's children" , "Mona ..., also called La Gioconda" .)