Stand-in about to star a game of tennis (7)
I believe the answer is:
reserve
'star a game of tennis' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'stand-in about' is the wordplay.
I cannot quite understand how this works, but
'about' could be 're' ('re' means regarding or about) and 're' is found within the answer.
The remaining letters 'serve' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'to' acts as a link.
Can you help me to learn more?
(Other definitions for reserve that I've seen before include "some distance" , "not in the front line" , "Keep for future use" , "Save" , "Keep back - book" .)