Discerning in saint a goodness, right away (9)
I believe the answer is:
sagacious
'discerning' is the definition.
(thesaurus)
'in saint a goodness right away' is the wordplay.
'in saint' becomes 's' (I am not sure about the 'in' bit.).
'goodness' becomes 'gracious' (both are expressions of shock).
'right' becomes 'r' (common abbreviation).
'away' suggests deleting specific letters.
'gracious' with 'r' taken out is 'gacious'.
's'+'a'+'gacious'='SAGACIOUS'
(Other definitions for sagacious that I've seen before include "Wise" , "Astute" .)