Notes barrier to self-preservation (7)
I believe the answer is:
defence
'self-preservation' is the definition.
(thesaurus)
'notes barrier' is the wordplay.
'notes' becomes 'de' (two musical notes).
'barrier' becomes 'fence' (fence is a kind of barrier).
'de'+'fence'='DEFENCE'
'to' is the link.
(Other definitions for defence that I've seen before include "Evidence from the accused" , "One ministry" , "See 12" , "barricade" , "Protection from harm" .)