Fine rank (5)
I believe the answer is:
sheer
I believe this clue is a double definition.
'fine' is the first definition.
(thesaurus)
'rank' is the second definition.
('sheer' can be a synonym of 'rank')
(Other definitions for sheer that I've seen before include "transparent fabric" , "Mere" , "Precipitous or fine" , "Gossamer or precipitous" , "Very fine or vertical" .)