As well; too (4)
I believe the answer is:
also
I believe this clue is a double definition.
'as well' is the first definition.
(synonyms)
'too' is the second definition.
(synonyms)
(Other definitions for also that I've seen before include "into the bargain" , "Furthermore" , "'Besides, moreover (4)'" , "Plus" , "As well, in addition" .)