Adult with young man dressed at last in rubber? (7)
I believe the answer is:
aladdin
'rubber?' is the definition.
(I've seen this before)
'adult with young man dressed at last in' is the wordplay.
'adult' becomes 'a' (abbreviation).
'with' says to put letters next to each other.
'young man' becomes 'lad' (I've seen this before).
'at last' suggests the final letters.
The last letter of 'dressed' is 'd'.
'a'+'lad'+'d'+'in'='ALADDIN'
(Other definitions for aladdin that I've seen before include "Pantomime set in China" , "Magic lamp rubber?" , "Panto character with magic lamp (7)" , "pantomime role" , "Pantomime boy with wonderful lamp" .)