Splendid bottle opener. Splendid! (6)
I believe the answer is:
superb
'splendid' is the definition.
(both can mean excellent)
'splendid bottle opener' is the wordplay.
'splendid' becomes 'super' (I've seen this before).
'opener' indicates taking the first letters.
The first letter of 'bottle' is 'b'.
'super'+'b'='SUPERB'
(Other definitions for superb that I've seen before include "First-class" , "Outstandingly excellent" , "Triumphantly effective" , "Magnificent, quite splendid" , "Dazzling" .)