A young man dressed finally in rubber? (7)
I believe the answer is:
aladdin
'rubber?' is the definition.
(Aladdin rubbed a magic lamp)
'a young man dressed finally in' is the wordplay.
'young man' becomes 'lad' (lad can mean a boy or young man).
'finally' says to take the final letters.
The final letter of 'dressed' is 'd'.
'a'+'lad'+'d'+'in'='ALADDIN'
(Other definitions for aladdin that I've seen before include "Common panto hero" , "Arabian Nights character with cave" , "Widow Twankey's principal boy" , "A 13 Down" , "Panto character with magic lamp (7)" .)