Lost for words as we crashed wagon (9)
(Other definitions for awestruck that I've seen before include "full of admiration" , "Wondering" , "Intimidated" , "overcome by wonder" , "Terrified" .)
'lost for words' is the definition.
(I've seen this before)
'as we crashed wagon' is the wordplay.
'crashed' indicates anagramming the letters.
'wagon' becomes 'truck'.
'as'+'we'='aswe'
'aswe' is an anagram of 'awes'.
'awes'+'truck'='AWE-STRUCK'
(Other definitions for awe-struck that I've seen before include "Smitten with wonder" , "Filled with reverential fear" , "Showing a feeling of wonder and dread" , "Lost for words" , "Suck water (anag) - completely astonished" .)