Those left right out for attendant (7)
I believe the answer is:
hostler
'attendant' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'those left right out' is the wordplay.
'left' becomes 'l' (common abbreviation).
'right' becomes 'r' (common abbreviation).
'out' indicates an anagram (out can mean wrong or inaccurate).
'those'+'l'+'r'='thoselr'
'thoselr' anagrammed gives 'HOSTLER'.
'for' acts as a link.
Can you help me to learn more?
(Another definition for hostler that I've seen is " service - I may supply it with rolling stock".)