Former Fed chairman Greenspan (4)
I believe the answer is:
alan
'former fed chairman greenspan' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alan that I've seen before include "A.A. Milne's first name" , "- Ayckbourn, English playwright" , "-- Sugar, British entrepreneur" , "- Bates, - Bennett" , "English historian/poet" .)