Best Actor of 1990 (5)
I believe the answer is:
'best actor of 1990' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for irons that I've seen before include "Metal-headed golfclubs" , "instruments of restraint" , "Smooths, presses" , "Jeremy ---, Br. actor; golf clubs" , "sporting equipment" .)