Fool with untruths about young women (7)

I believe the answer is:

lassies

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'young women' is the definition.
(I've seen this before)

'fool with untruths about' is the wordplay.
'fool with' becomes 'ass' (both can mean a stupid person. I am not sure about the 'with' bit.).
'untruths' becomes 'lies' (lie is a kind of untruth).
'about' means one lot of letters goes inside another.
'ass' going inside 'lies' is 'LASSIES'.

Can you help me to learn more?

(Other definitions for lassies that I've seen before include "Wee Scottish girls" , "Young women" .)

I've seen this clue in The Telegraph.

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