University plugging dissertations in ancient Greek (7)
I believe the answer is:
theseus
'ancient greek' is the definition.
(I've seen this before)
'university plugging dissertations' is the wordplay.
'university' becomes 'U' (abbreviation for university).
'plugging' indicates putting letters inside (inserted letters plug up a gap in the word).
'dissertations' becomes 'theses' ('thesis' can be a synonym of 'dissertation').
'u' going into 'theses' is 'THESEUS'.
'in' acts as a link.
(Other definitions for theseus that I've seen before include "Mythological hero" , "Rescuer of Ariadne" , "Mythical hero" , "Attic hero" , "authority in the D [DREAM]" .)