Mean lass upset one taking orders (8)
I believe the answer is:
salesman
'one taking orders' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'mean lass upset' is the wordplay.
'upset' indicates an anagram.
'mean'+'lass'='meanlass'
'meanlass' anagrammed gives 'SALESMAN'.
Can you help me to learn more?
(Other definitions for salesman that I've seen before include "Arthur Miller wrote 'Death of a . . . . . . . .'" , "He's a vendor" , "He sells lean mass, strangley" , "He sells lean mass, oddly" , "Travelling rep" .)