Just you watch it ... don't be a part of their game (9,5)
I believe the answer is:
spectator sport
'just you watch' is the definition.
The definition suggests a singular noun which matches the answer.
'it don't be a part of their game' is the wordplay.
I cannot really see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
'a' is within the answer.
'of' could be 'o' and 'o' is present in the answer.
'game' could be 'p' (I have seen 'French game ' mean 'p' so perhaps 'game' could also mean 'p') and 'p' 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 spectator sport that I've seen before include "something to watch" , "Eg, football" , "For example, cricket" , "You're not invited to join in this" , "one to watch" .)