Lover's song composed, welcoming publicity (8)
I believe the answer is:
serenade
'lover's song' is the definition.
(I've seen this before)
'composed welcoming publicity' is the wordplay.
'composed' becomes 'serene' (I've seen this in other clues).
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'publicity' becomes 'ad' (short for advert).
'serene' enclosing 'ad' is 'SERENADE'.
(Other definitions for serenade that I've seen before include "Piece sung beneath beloved's window" , "It's played or sung at a lover's window" , "Open-air song" , "Evening love song" , "Suitor's song" .)