Rumour of cut being steep (5)
I believe the answer is:
sheer
'being steep' is the definition.
('sheer' can be similar in meaning to 'steep')
'rumour of cut' is the wordplay.
'rumour of' shows a homophone (sound like).
'cut' becomes 'shear' (shearing is a kind of cutting).
'shear' is a homophone of 'SHEER'.
(Other definitions for sheer that I've seen before include "Very steep - may apply to 4" , "Very fine or vertical" , "Utter - precipitous" , "Very steep or diaphanous" , "Film" .)