Indeed, really (5)
I believe the answer is:
truly
This clue is a double definition.
'indeed' is the first definition.
(synonyms)
'really' is the second definition.
(I know that really can be written as truly)
(Other definitions for truly that I've seen before include "Verily" , "Honestly" , "Genuinely, properly" , "Really, genuinely" , "Indeed" .)