Pictures youngsters keep at home? (3-3)
I believe the answer is:
pin-ups
'pictures' is the definition.
(I've seen this before)
'youngsters keep at home?' is the wordplay.
'youngsters' becomes 'pups'.
'keep' indicates putting letters inside.
'at home?' becomes 'in' ('I'm in' can mean 'I'm at home').
'pups' placed around 'in' is 'PIN-UPS'.
(Other definitions for pin-ups that I've seen before include "They may be very pretty" , "Posters of stars" , "Cover girls" .)