The rugby game's finished lacking players (2,4)
I believe the answer is:
no side
'the rugby' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's a link between them I don't understand?
'game's finished lacking players' is the wordplay.
I cannot quite see how this works, but
'lacking' could be 'no' (eg lacking money means with no money) and 'no' is present in the answer.
'players' could be 'side' (eg a football side) and 'side' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for no side that I've seen before include "time to leave field of activity" , "For rugby players the end" , "end of rugby match" , "End of a rugby game" .)