Glowing girl initially ashamed during harangue (7)
I believe the answer is:
radiant
'glowing' is the definition.
(thesaurus)
'girl initially ashamed during harangue' is the wordplay.
'girl' becomes 'di'.
'initially' suggests taking the first letters.
'during' is an insertion indicator.
'harangue' becomes 'rant' ('rant' can be a synonym of 'harangue').
The first letter of 'ashamed' is 'a'.
'di'+'a'='dia'
'dia' inserted into 'rant' is 'RADIANT'.
(Other definitions for radiant that I've seen before include "Sending out light, glowing" , "Dazzling" , "Lit up" , "Bright" , "Splendid; heater type" .)