Dissertation by a professional added limb (10)
I believe the answer is:
prosthesis
'limb' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'dissertation by a professional added' is the wordplay.
'dissertation' becomes 'thesis' (synonyms).
'by' says to put letters next to each other.
'a professional' becomes 'pro' (abbreviation).
'added' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'pro'+'s'='pros'
'thesis' put after 'pros' is 'PROSTHESIS'.
Can you help me to learn more?
(Other definitions for prosthesis that I've seen before include "Artificial body-part" , "artificial substitute" , "This may supply missing part" , "what can help a handicapped person" , "Artificial body part" .)