Rambling rose, but more dull (7)
I believe the answer is:
obtuser
'more dull' is the definition.
(I've seen this before)
'rambling rose but' is the wordplay.
'rambling' is an anagram indicator.
'rose'+'but'='rosebut'
'rosebut' anagrammed gives 'OBTUSER'.
(Other definitions for obtuser that I've seen before include "More dumb" , "More insensitive" , "More dull" , "Comparatively stupid" .)