Publicise, year upon year, entertainment of a delicate nature (4-5)
I believe the answer is:
airy-fairy
'of a delicate nature' is the definition.
(both can mean fancy or elegant)
'publicise year upon year entertainment' is the wordplay.
'publicise' becomes 'air' (airing is a kind of publicising).
'year' becomes 'y'.
'upon' says to put letters next to each other.
'year' becomes 'y'.
'entertainment' becomes 'fair' (as in a fun fair).
'y' put after 'fair' is 'fairy'.
'air'+'y'+'fairy'='AIRY-FAIRY'
(Other definitions for airy-fairy that I've seen before include "Fanciful and impractical like breezy sprite" , "Unrealistic - fanciful" , "Fanciful, not based on reality" , "Lightweight" , "Fanciful or impractical for breezy elf" .)