Wins at chess (5)
'wins at chess' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mates that I've seen before include "Friends among the ship's officers" , "Pals, pairs" , "Naval officers'" , "Pals or spouses" , "Partners or pals" .)
(Other definitions for materials that I've seen before include "Items needed to tackle a job" , "See 10" , "textiles" , "Substances that go into the making something" .)