Intimate duo ultimately can't find convertible (9)
I believe the answer is:
confidant
'intimate' is the definition.
('confidant' can be a synonym of 'intimate')
'duo ultimately can't find convertible' is the wordplay.
'ultimately' says to take the final letters.
'convertible' is an anagram indicator.
The final letter of 'duo' is 'o'.
'o'+'cant'+'find'='ocantfind'
'ocantfind' with letters rearranged gives 'CONFIDANT'.
(Other definitions for confidant that I've seen before include "Trusted friend" , "intimate" , "Close friend entrusted with secrets etc" , "Sharer of secrets" .)