Tube repairer apparently erred at the finish, we hear (4,4)
I believe the answer is:
duct tape
'tube repairer' is the definition.
(tape used to repair ducts or tubes)
'apparently erred at the finish we hear' is the wordplay.
I cannot really see how this works, but
'apparently' could be 'ap' (I've seen this in other clues) and 'ap' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
This explanation may well be incorrect...
(Another definition for duct tape that I've seen is " What may reduce leaks".)