A throw in? Yes and no! (4-3)
I believe the answer is:
line-out
'a throw' is the definition.
Both the answer and definition are singular nouns.
Maybe there's an association between them I don't understand?
'in? yes and no' is the wordplay.
I cannot really understand how this works, but
'in?' could be 'in' and 'in' is found in the answer.
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for line-out that I've seen before include "RU throw-in" , "Rugby re-start" , "A rugby formation to receive throw-in" , "A standing rugby formation" , "Set piece of play in rugby" .)