Side street boy (3)
I believe the answer is:
des
'boy' is the definition.
(short for Desmond)
'side street' is the wordplay.
'DES' is hidden within the letters.
However, I'm unsure how this is indicated.
Can you help me to learn more?
(Other definitions for des that I've seen before include "- O'Connor, Br. singer" , "and 9 Across: Former 'Countdown' host" .)