Don's trendy joint is a club promising camaraderie (10)
I believe the answer is:
fellowship
'camaraderie' is the definition.
(I've seen this before)
'don's trendy joint' is the wordplay.
'don's' becomes 'fellows' (I can't explain this - if you can you should give a lot more credence to this answer).
'trendy joint' becomes 'hip' (I've seen this before).
'fellows'+'hip'='FELLOWSHIP'
'is a club promising' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for fellowship that I've seen before include "Association" , "camaraderie" , "club" , "Academic honour" , "Friendliness; guild" .)