Breeze along full of enthusiasm (4)
I believe the answer is:
zeal
'enthusiasm' is the definition.
(I know that zeal is a type of avidity)
'breeze along full of' is the wordplay.
'full of' indicates a hidden word (inside).
'ZEAL' is hidden within 'breeze along'.
(Other definitions for zeal that I've seen before include "(Excessive) fervour" , "Extreme enthusiasm" , "6 [ENTHUSIASM]" , "Interest that's definitely not diminished" , "Verve" .)