Deeply impressed, one day (4)
I believe the answer is:
awed
'deeply impressed' is the definition.
(I've seen this in another clue)
'one day' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'day' becomes 'wed' (abbreviation for Wednesday).
'a'+'wed'='AWED'
(Other definitions for awed that I've seen before include "Made to feel fear/wonder" , "was dazzling" , "in wonderment" , "Inspired with reverence" , "Filled with reverential wonder" .)