Swindle at seat of Irish kings? A harmless lie (10)

I believe the answer is:

taradiddle

I'm a little stuck... Click here to teach me more about this clue!

'a harmless lie' is the definition.
'taradiddle' can be an answer for 'lie' (thesaurus). I am not certain of the 'a harmless' bit.

'swindle at seat of irish kings?' is the wordplay.
'swindle' becomes 'diddle' (synonyms).
'at' means one lot of letters go next to another (I've seen this in other clues).
'seat of irish kings?' becomes 'tara' (I've seen this in another clue).
'diddle' put after 'tara' is 'TARADIDDLE'.

Can you help me to learn more?

(Other definitions for taradiddle that I've seen before include "Nonsense" , "Tripe" , "Fiddlesticks!" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.