Tycoon requires new gateman (7)
I believe the answer is:
magnate
'tycoon' is the definition.
(I know that tycoon can be written as magnate)
'new gateman' is the wordplay.
'new' is an anagram indicator.
'gateman' anagrammed gives 'MAGNATE'.
'requires' is the link.
(Other definitions for magnate that I've seen before include "Baron" , "Wealthy figure" , "Mogul" , "Important fellow" , "Wealthy business leader" .)