Young men found old Penny in the little girls' room (7)
I believe the answer is:
laddies
'young men' is the definition.
(I've seen this before)
'old penny in the little girls' room' is the wordplay.
'old penny' becomes 'd'.
'in the' is an insertion indicator.
'little girls' room' becomes 'ladies' (I can't justify this - if you can you should believe this answer much more).
'd' going into 'ladies' is 'LADDIES'.
'found' is the link.
Can you help me to learn more?
(Other definitions for laddies that I've seen before include "young men" , "Boys" .)