Authorises at last the transplantation of the roses (8)
I believe the answer is:
endorses
'authorises at last the transplantation of the roses' is the definition.
I can't judge whether this definition defines the answer.
'authorises at last the transplantation' is the wordplay.
'authorises' becomes 'dorses' (I can't explain this - if you can you should believe this answer much more).
'at' means one lot of letters go next to another (I've seen this in other clues).
'last' says to take the final letters.
The last letters of 'the transplantation' are 'en'.
'dorses' after 'en' is 'ENDORSES'.
Can you help me to learn more?
(Other definitions for endorses that I've seen before include "'Supports, backs (8)'" , "One dress (anag.)" , "Approves, supports" , "Countersigns, approves" , "Gives support or approval to" .)