Excessively as well (3)
I believe the answer is:
too
I believe this clue is a double definition.
'excessively' is the first definition.
(to too great a degree)
'as well' is the second definition.
(both can mean 'also')
(Other definitions for too that I've seen before include "Also; overly" , "Excessively" , "Likewise" , "On top - also" , "To a greater than desirable extent" .)