Sweeping statement sadly alienating Rose (14)
I believe the answer is:
generalisation
'sweeping statement' is the definition.
(I've seen this before)
'sadly alienating rose' is the wordplay.
'sadly' indicates anagramming the letters.
'alienating'+'rose'='alienatingrose'
'alienatingrose' anagrammed gives 'GENERALISATION'.
(Other definitions for generalisation that I've seen before include "sweeping statement" , "that has nothing specific to say" .)