Fine, very steep (5)
I believe the answer is:
I believe this clue is a double definition.
'fine' is the first definition.
(I've seen this before)
'very steep' is the second definition.
(I've seen this in another clue)
(Other definitions for sheer that I've seen before include "Absolutely - diaphanous" , "Completely" , "transparent fabric" , "Deviate (from) - vertical" , "Very steep; utter" .)