One who is likely to repeat usual rubbish (6)
I believe the answer is:
parrot
'one who is likely to repeat' is the definition.
(I know this)
'usual rubbish' is the wordplay.
'usual' becomes 'par' (par is an average golf score).
'rubbish' becomes 'rot' (both can mean nonsense).
'par'+'rot'='PARROT'
(Other definitions for parrot that I've seen before include "Vividly coloured bird" , "Eg, macaw" , "Bird (that repeats)" , "Bright tropical bird" , "Repeat without understanding" .)