Astonished, inveighs against delivery vehicle (13)

I believe the answer is:

thunderstruck

'astonished' is the definition.
(synonyms)

'inveighs against delivery vehicle' is the wordplay.
'inveighs against' becomes 'thunders' (to thunder against an idea is to speak against it).
'delivery vehicle' becomes 'truck'.
'thunders'+'truck'='THUNDERSTRUCK'

(Other definitions for thunderstruck that I've seen before include "Flabbergasted" , "Amazed" , "Completely taken aback" , "Stupefied" , "can't speak?" .)

I've seen this clue in The Times.

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