Repeat what is expected — rubbish (6)
I believe the answer is:
parrot
'repeat' is the definition.
(I know that parrot is a more specific form of the action repeat)
'expected rubbish' is the wordplay.
'expected' becomes 'par' (as in 'par for the course').
'rubbish' becomes 'rot' (both can mean nonsense).
'par'+'rot'='PARROT'
'what is' acts as a link.
(Other definitions for parrot that I've seen before include "birdie" , "Tropical bird to repeat mindlessly" , "Tropical bird, may talk" , "Vividly coloured bird" , "Repeat unintelligently" .)