Stop showing a boy it's wrong (6)
I believe the answer is:
desist
'stop' is the definition.
(desist means to stop)
'a boy it's wrong' is the wordplay.
'a boy' becomes 'des' (short for Desmond).
'wrong' is an anagram indicator.
'its' anagrammed gives 'ist'.
'des'+'ist'='DESIST'
'showing' acts as a link.
(Other definitions for desist that I've seen before include "'Refrain from, stop (6)'" , "Forbear" , "Whoa, cease" , "Abstain, refrain" , "Leave off (doing a thing)" .)