As well as excessively (3)
I believe the answer is:
too
I believe this clue is a double definition.
'as well as' is the first definition.
(I've seen this in another clue)
'excessively' is the second definition.
(to too great a degree)
(Other definitions for too that I've seen before include "What a pity!" , "As well; in addition" , "On top - also" , "As well, also" , "Moreover, in addition" .)