Rob Holding - fellow party animal (8)
I believe the answer is:
hedonist
'party animal' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'rob holding fellow' is the wordplay.
'rob' becomes 'heist' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'holding' means one lot of letters goes inside another.
'fellow' becomes 'don' (both can mean an academic).
'heist' enclosing 'don' is 'HEDONIST'.
Can you help me to learn more?
(Other definitions for hedonist that I've seen before include "Thrill-seeker" , "Seeker of sensual pleasure" , "one enjoying himself" , "Epicurean" , "One who believes in pleasure" .)