A fellow with plenty of time to run a business (6)
I believe the answer is:
manage
'run a business' is the definition.
(I've seen this in another clue)
'a fellow with plenty of time' is the wordplay.
'a fellow with' becomes 'man' (I've seen this in other clues).
'plenty of time' becomes 'age' (I've seen this before).
'man'+'age'='MANAGE'
'to' acts as a link.
(Other definitions for manage that I've seen before include "Handle, oversee" , "Exercise control - don't fail" , "Take control" , "Run, administer" , "Run (a football team)" .)