Girl coming out from sideboard (3)
I believe the answer is:
'girl coming out' is the definition.
(short for debutante)
'from sideboard' is the wordplay.
'from' indicates the answer is hidden within the clue.
'DEB' can be found hidden inside 'sideboard'.
(Other definitions for deb that I've seen before include "In brief, a society girl getting out of bed" , "Girl just entering society" , "Young socialite" , "Young woman making her first appearance in society, in short" , "One coming out" .)