Slippery, perhaps, and grey as can be (6)
I believe the answer is:
greasy
'slippery' is the definition.
(similar in meaning)
'and grey as can be' is the wordplay.
'grey as' anagrams to 'GREASY'.
But, I'm not clear how this is indicated.
'perhaps' acts as a link.
Can you help me to learn more?
(Other definitions for greasy that I've seen before include "Covered in oil" , "well-lubricated" , "Thickly oleaginous" , "Unctuous or ingratiating" , "Like the pole that is hard to climb" .)