Chess players seek these partners (5)
I believe the answer is:
mates
'these partners' is the definition.
('mate' can be a synonym of 'partner')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for mates that I've seen before include "Friends among the ship's officers" , "Naval officers'" , "Pals or spouses" , "Chums" , "conclusive moves on board" .)