Sack irrational salesperson lying about tattoo artist (8)
I believe the answer is:
bagpiper
'tattoo artist' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'sack irrational salesperson lying about' is the wordplay.
'sack' becomes 'bag' (I've seen this in another clue).
'irrational' becomes 'pi' (an irrational number).
'salesperson lying' becomes 'rep' (I can't explain this - if you can you should give a lot more credence to this answer).
'about' says the letters should be written backwards.
'rep' written backwards gives 'per'.
'bag'+'pi'+'per'='BAGPIPER'
Can you help me to learn more?
(Other definitions for bagpiper that I've seen before include "One blows out air" , "Scots musician" , "Wind musician" , "Pibroch player" , "Player of traditional Scottish musical instrument" .)