Get a man mixed up with big business (7)
I believe the answer is:
magnate
'big business' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I can't see?
'get a man mixed up' is the wordplay.
'mixed up' indicates anagramming the letters.
'get'+'a'+'man'='getaman'
'getaman' is an anagram of 'MAGNATE'.
'with' is the link.
Can you help me to learn more?
(Other definitions for magnate that I've seen before include "Mogul" , "Fat cat" , "Fellow with a lot of money" , "Wealthy figure" , "Baron" .)