Amateur snooker player pockets red, shortly (8)
I believe the answer is:
potterer
'amateur' is the definition.
(thesaurus)
'snooker player pockets red shortly' is the wordplay.
'snooker player' becomes 'potter' (pots balls).
'pockets' is an insertion indicator.
'shortly' means to remove the last letter.
'red' with its last letter taken away is 're'.
'potter' going around 're' is 'POTTERER'.
(Other definitions for potterer that I've seen before include "One who moves in an unhurried way" , "fiddler" , "who only dabbles" .)