Wrap frayed rope in skin — it makes it last longer (8)
I believe the answer is:
foreplay
'it makes it last longer' is the definition.
(something which makes sex - 'it' - last longer)
'wrap frayed rope in' is the wordplay.
'wrap' becomes 'flay' (I can't explain this - if you can you should give a lot more credence to this answer).
'frayed' indicates anagramming the letters.
'in' indicates putting letters inside.
'rope' is an anagram of 'orep'.
'flay' placed around 'orep' is 'FOREPLAY'.
'skin' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for foreplay that I've seen before include "Sexual preamble" , "Precursor to main action" .)