A jam, when tennis player keeps bouncing the ball (8)
I believe the answer is:
preserve
'a jam' is the definition.
(jam is a type of preserve)
'tennis player keeps bouncing the ball' is the wordplay.
I cannot quite understand how this works, but
'player' could be 'reserve' (I've seen this before) and 'reserve' is present in the answer.
A single letter 'p' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'when' acts as a link.
Can you help me to learn more?
(Other definitions for preserve that I've seen before include "Maintain - jam" , "Jam; safeguard" , "Keep safe or in unchanged condition" , "Prevent from rotting" , "Maintain in unaltered condition" .)