Safe to sleep around to obtain eternal youth? (5,3)
I believe the answer is:
peter pan
'eternal youth?' is the definition.
'safe to sleep around' is the wordplay.
'safe' becomes 'peter' (slang term for a safe).
'to sleep' becomes 'nap' (a nap is a short sleep).
'around' says the letters should be written in reverse.
'nap' back-to-front is 'pan'.
'peter'+'pan'='PETER PAN'
'to obtain' acts as a link.
(Other definitions for peter pan that I've seen before include "Barrie's ageless youth" , "D [Disney] made" , "Kind of collar for" , "Child that never grows old" , "J. M. Barrie's hero" .)