Slick cat almost rampant? (3)
I believe the answer is:
oil
'slick' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for oil that I've seen before include "Viscous substance as lubricant" , "Fluid lubricant" , "Thick liquid that doesn't dissolve in water" , "Greasy liquid" , "Liquid gold" .)