Astonishing success, wearing silver (5)
I believe the answer is:
awing
'astonishing' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
'success wearing silver' is the wordplay.
'success' becomes 'win' (I've seen this in another clue).
'wearing' is an insertion indicator.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'win' inserted into 'ag' is 'AWING'.
Can you help me to learn more?
(Other definitions for awing that I've seen before include "inspiring great admiration" , "producing reverence" , "Causing dread" , "Inspiring reverence" , "Creating reverence" .)