Running back is claiming tennis champion is silent (9)
I believe the answer is:
noiseless
'silent' is the definition.
(I've seen this before)
'running back is claiming tennis champion is' is the wordplay.
'running' becomes 'on' (eg when a machine is running it is on).
'back' says the letters should be written in reverse.
'is claiming' means one lot of letters goes inside another.
'tennis champion' becomes 'seles' (I can't justify this - if you can you should believe this answer much more).
'on' backwards is 'no'.
'seles' placed into 'is' is 'iseless'.
'no'+'iseless'='NOISELESS'
Can you help me to learn more?
(Other definitions for noiseless that I've seen before include "Lionesses (anag) - making no sound" , "unsound?" , "with a silencer?" , "Mum" , "Silent, quiet" .)