Supported conclusion - rose sadly died (8)
I believe the answer is:
endorsed
'supported' is the definition.
(endorsing is a kind of supporting)
'conclusion rose sadly died' is the wordplay.
'conclusion' becomes 'end' (something's conclusion is its end).
'sadly' indicates an anagram.
'died' becomes 'd' (abbreviation next to the year of someone's death).
'rose' with letters rearranged gives '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" .)