Like burning rubber (5)
I believe the answer is:
acrid
'like burning rubber' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for acrid that I've seen before include "Strong and sharp" , "Strong and sharp-smelling" , "Bitterly pungent" , "Bitter in smell, like smoke" , "Bitter or corrosive" .)