in an impassive manner (8)
I believe the answer is:
stolidly
'in an impassive manner' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stolidly that I've seen before include "In unemotional manner" , "without great enthusiasm?" , "In an impassive manner" , "Showing no interest" , "Without feeling" .)