Dissertation from expert, not an original member? (10)
I believe the answer is:
prosthesis
'not an original member?' is the definition.
(a replacement for an amputated member)
'dissertation from expert' is the wordplay.
I cannot quite see how this works, but
'dissertation' could be 'thesis' (synonyms) and 'thesis' is located in the answer.
'expert' could be 'pro' (I've seen this before) and 'pro' is found in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for prosthesis that I've seen before include "Part replacement" , "what can help a handicapped person" , "Artificial body part" , "This may supply missing part" , "artificial substitute" .)