Passing time with artist playing tennis (9)
I believe the answer is:
transient
'passing' is the definition.
('transient' can be a synonym of 'passing')
'time with artist playing tennis' is the wordplay.
'time' becomes 't' (**).
'with' indicates putting letters inside.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'playing' is an anagram indicator.
'tennis' anagrammed gives 'nsient'.
'ra' put inside 'nsient' is 'ransient'.
't'+'ransient'='TRANSIENT'
(Other definitions for transient that I've seen before include "Fleeting" , "on the move" , "Here today, gone tomorrow" , "gone in a trice!" , "Lasting little time" .)