Exhausted fellow with little energy (4)
I believe the answer is:
done
'exhausted' is the definition.
(thesaurus)
'fellow with little energy' is the wordplay.
'fellow' becomes 'don' (both can mean an academic).
'with' means one lot of letters go next to another.
'little' indicates taking the first letters.
The first letter of 'energy' is 'e'.
'don'+'e'='DONE'
(Other definitions for done that I've seen before include "Completed" , "Thoroughly cooked; accomplished" , "Complete; finished" , "This settled" , "Artist's workroom" .)