Boy going round yard snooping (4)
I believe the answer is:
nosy
'snooping' is the definition.
(thesaurus)
'boy going round yard' is the wordplay.
'boy' becomes 'son' ('son' can be a synonym of 'boy'**).
'going round' says the letters should be written in reverse.
'yard' becomes 'y'.
'son' back-to-front is 'nos'.
'nos'+'y'='NOSY'
(Other definitions for nosy that I've seen before include "Prying, snoopy" , "lots of questions" , "Showing too much curiosity about people's affairs" , "Inclined to poke into other people's affairs" , "Inquisitive in nasal manner" .)