Actually; very (6)
I believe the answer is:
really
I believe this clue is a double definition.
'actually' is the first definition.
(I know that actually can be written as really)
'very' is the second definition.
(I know that very can be written as really)
(Other definitions for really that I've seen before include "surely not?" , "Do you mean it?" , "Dead" , "without a doubt" , "Undoubtedly" .)