Shyness in manner shown by good person to boy in the end (7)
I believe the answer is:
modesty
'shyness' is the definition.
(thesaurus)
'manner shown by good person to boy in the end' is the wordplay.
'manner' becomes 'mode' (synonyms).
'shown by' is a charade indicator (letters next to each other).
'good person' becomes 'st' (saint).
'to' means one lot of letters go next to another.
'in the end' says to take the final letters.
The final letter of 'boy' is 'y'.
'mode'+'st'+'y'='MODESTY'
'in' acts as a link.
(Other definitions for modesty that I've seen before include "Humility; decency" , "Reserve" , "lack of vanity" , "Self-deprecating quality" , "Quality of being unpretentious" .)