Sack irrational salesperson lying about tattoo artist (8)
I believe the answer is:
bagpiper
'tattoo artist' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'sack irrational salesperson lying about' is the wordplay.
'sack' becomes 'bag' (I've seen this before).
'irrational' becomes 'pi' (an irrational number).
'salesperson lying' becomes 'rep' (I can't justify this - if you can you should give a lot more credence to this answer).
'about' is a reversal indicator.
'rep' back-to-front is '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" .)