Such men may take turns as openers (3)
I believe the answer is:
key
'such' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I can't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for key that I've seen before include "Scale system for music" , "Eg, Ctrl, Alt or Esc" , "Device for lock" , "It can open" , "Of crucial importance" .)