Bit of fun following the blue bird (7)
I believe the answer is:
skylark
'bird' is the definition.
(skylark is a kind of bird)
'bit of fun following the blue' is the wordplay.
'bit of fun' becomes 'lark' (I've seen this before).
'following' is a charade indicator (letters next to each other).
'the blue' becomes 'sky' (I've seen this in other clues).
'lark' put after 'sky' is 'SKYLARK'.
(Other definitions for skylark that I've seen before include "Play jokes" , "Bird (of 23?)" , "Play boisterously" , "High-flying songbird" , "Flyer" .)