Carried by motorcar, pets wee periodically -- cleaner needed! (6-7)
I believe the answer is:
carpet sweeper
'cleaner needed' is the definition.
(device for cleaning)
'carried by motorcar pets wee periodically' is the wordplay.
'carried by' indicates a hidden word.
'CARPET-SWEEPER' is hidden within 'motorcar pets wee periodically'.
(Other definitions for carpet sweeper that I've seen before include "cleaning device" , "Household appliance" , "Domestic cleaning equipment" , "Floor cleaner" , "Cleaning equipment - we respect a rep (anag)" .)