Blue tit's fancy secondary name (8)
I believe the answer is:
subtitle
'secondary name' is the definition.
(subtitle can mean an additional title)
'blue tit's fancy' is the wordplay.
'fancy' is an anagram indicator.
'blue'+'tits'='bluetits'
'bluetits' is an anagram of 'SUBTITLE'.
(Other definitions for subtitle that I've seen before include "Translation of foreign dialogue, displayed at the bottom of the screen" , "A subordinate caption as under foreign film" , "It appears on screen in a foreign-language film" , "Word found at bottom of movie or TV screen" , "Translation of foreign dialogue, in a movie say" .)