Street vehicle in task removing what is grotty, ultimately? (8)
I believe the answer is:
dustcart
'task removing what is grotty ultimately?' is the definition.
I can't tell whether this definition defines the answer.
'street vehicle' is the wordplay.
'street' becomes 'dust' (I can't explain this - if you can you should give a lot more credence to this answer).
'vehicle' becomes 'cart' (cart is a kind of vehicle).
'dust'+'cart'='DUSTCART'
'in' is the link.
(Other definitions for dustcart that I've seen before include "Refuse collector" , "Rubbish-collecting vehicle" , "Vehicle for collecting rubbish" , "Refuse vehicle" , "Council vehicle" .)