Rough as a diamond? (5)
I believe the answer is:
uncut
This clue is a double definition.
'rough' is the first definition.
('uncut' can be a synonym of 'rough')
'as a diamond?' is the second definition.
(some diamonds are uncut)
(Other definitions for uncut that I've seen before include "(Of a diamond) rough" , "diamonds, originally" , "Without abridgement" , "Like diamonds, initially" , "Not edited" .)