A throw in? Yes and no! (4-3)
I believe the answer is:
line-out
'a throw' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'in? yes and no' is the wordplay.
I cannot quite understand how this works, but
'in?' could be 'in' and 'in' is located in the answer.
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is found 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" .)