A player may need a rest when operating on this (8,5)
I believe the answer is:
billiard table
'a rest when operating on this' is the definition.
The definition suggests a singular noun which matches the answer.
'a player may need' is the wordplay.
'a player' becomes 'billiard' (billiard player is a kind of player).
'may need' becomes 'table' (I can't justify this - if you can you should believe this answer much more).
'billiard'+'table'='BILLIARD-TABLE'
Can you help me to learn more?
(Other definitions for billiard table that I've seen before include "Large flat item used for indoor game" , "Flat baize-covered surface with pockets" , "On which cues are used" , "Surface for pool, snooker, etc" , "Smooth indoor "sporting" surface" .)