Supported conclusion - rose sadly died (8)
I believe the answer is:
endorsed
'supported' is the definition.
('endorse' can be a synonym of 'support')
'conclusion rose sadly died' is the wordplay.
'conclusion' becomes 'end' (end is a kind of conclusion**).
'sadly' indicates anagramming the letters.
'died' becomes 'd'.
'rose' is an anagram of 'orse'.
'end'+'orse'+'d'='ENDORSED'
(Other definitions for endorsed that I've seen before include "Signed one's name to certify" , "Confirmed a statement or signed back of cheque" , "Certified or supported" , "Seconded" , "Given public approval" .)