Magnate (5)
I believe the answer is:
mogul
'magnate' is the definition.
(I know that magnate can be written as mogul)
This is all the clue.
(Other definitions for mogul that I've seen before include "Mr Big?" , "Powerful person, potentate" , "bigwig" , "Big cheese - mound of hard snow on a ski slope" , "Powerful businessperson" .)