How a realist would act, almost (11)
I believe the answer is:
practically
I believe this clue is a double definition.
'how a realist would act' is the first definition.
(a realist acts in a practical way)
'almost' is the second definition.
(I know that almost can be written as practically)
(Other definitions for practically that I've seen before include "how DIY expert approaches his work?" , "Almost" , "To all intents and purposes" , "how realist thinks" .)