Fuss shown by old man over former tennis star (7)
I believe the answer is:
palaver
'fuss' is the definition.
(both can mean a commotion)
'by old man over former tennis star' is the wordplay.
'by' means one lot of letters go next to another.
'old man' becomes 'pa' (both can mean someone's father).
'over former tennis star' becomes 'laver' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pa' next to 'laver' is 'PALAVER'.
'shown' acts as a link.
Can you help me to learn more?
(Other definitions for palaver that I've seen before include "Kind of discussion or idle chatter" , "Rabbit" , "Prolonged fuss" , "Commotion" , "Song-and-dance" .)