Calm, having a note to sing (8)
I believe the answer is:
serenade
'sing' is the definition.
(I've seen this before)
'calm having a note' is the wordplay.
'calm' becomes 'serene' (synonyms).
'having' indicates putting letters inside.
'note' becomes 'D' (musical note).
'a'+'d'='ad'
'serene' enclosing 'ad' is 'SERENADE'.
'to' is the link.
(Other definitions for serenade that I've seen before include "Suitor's song" , "composition" , "Song sung by suitor" , "Evening music (played outside woman's house)" , "Music played by lover" .)