It can blacken the character of a boy getting out of line (5)
I believe the answer is:
stain
'line' is the definition.
(thesaurus)
'it can blacken the character of a boy getting' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
'character' could be 's' and 's' is located in the answer.
'a' is found in the answer.
The remaining letters 'in' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'out of' acts as a link.
Can you help me to learn more?
(Other definitions for stain that I've seen before include "Smear" , "Colour, dye" , "Discolouration" , "Discoloured patch" , "Blemish; colour (wood)" .)