Good-as-new tires (8)
I believe the answer is:
'good-as-new tires' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for retreads that I've seen before include "recovered tyres" , "Serrated like tyres restored for use" , "Arrested over resurfaced tyres" , "They gain fresh employment" , "Serrated like remoulded tyres" .)