Coot (6)
I believe the answer is:
geezer
'coot' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for geezer that I've seen before include "Old eccentric chap" , "Fellow (slang)" , "Man (slang)" , "Old man (sl)" , "Eccentric man, usually old" .)