At a loss for words (6-4)
(Other definitions for speechless that I've seen before include "Lost for words" , "Dumbstruck" , "Dumbfounded" , "being forced to improvise?" , "Unable to say anything" .)
(Other definitions for awed that I've seen before include "in terror" , "Struck with fear/wonder" , "in wonderment" , "Seriously impressed" , "Inspired with wonder" .)
(Another definition for dumbfounded that I've seen is " Gobsmacked".)
'at a loss for words' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tongue-tied that I've seen before include "(Out of shyness) barely able to speak" , "Unable to say" , "Speechless with shyness" , "Speechless from embarrassment" , "Unable to speak coherently" .)