Courageous not finishing last of tobacco — well done! (5)
I believe the answer is:
bravo
'well done' is the definition.
(I've seen this before)
'courageous not finishing last of tobacco' is the wordplay.
'courageous' becomes 'brave' ('brave' can be a synonym of 'courageous').
'not finishing' means to remove the last letter.
'last of' suggests the final letters.
The last letter of 'tobacco' is 'o'.
'brave' with its final letter taken away is 'brav'.
'brav'+'o'='BRAVO'
(Other definitions for bravo that I've seen before include "Radio code word for B" , "Hurrah!" , "Exclamation of approval" , "Good man, well done" , "A cry meaning well done" .)