See-through fleece, we hear (5)
I believe the answer is:
sheer
'see-through' is the definition.
(I know that see-through can be written as sheer)
'fleece we hear' is the wordplay.
'fleece' becomes 'shear' (synonyms).
'we hear' shows a homophone (sound like).
'shear' sounds like 'SHEER'.
(Other definitions for sheer that I've seen before include "Transparently thin - very steep" , "Utter - precipitous" , "Film" , "Arrant" , "Absolute - precipitous" .)