Orchestra leader goes after wind to show enthusiasm (5)
I believe the answer is:
gusto
'enthusiasm' is the definition.
(gusto is a kind of enthusiasm)
'orchestra leader goes after wind' is the wordplay.
'leader' indicates taking the first letters.
'goes after' says to put letters next to each other.
'wind' becomes 'gust' (gust of wind).
The first letter of 'orchestra' is 'o'.
'o' put after 'gust' is 'GUSTO'.
'to show' acts as a link.
(Other definitions for gusto that I've seen before include "Zest, pleasure in action" , "Hearty enjoyment" , "ardour" , "Verve, zest" , "Exuberant enjoyment" .)