Spirit a little melancholy (4)
I believe the answer is:
elan
'spirit' is the definition.
(I know that elan is a type of spirit)
'a little melancholy' is the wordplay.
'a little' indicates the answer is hidden within the clue.
'ELAN' is hidden in the letters of 'melancholy'.
(Other definitions for elan that I've seen before include "spirit" , "Dash and enthusiasm." , "Combination of style and vigour" , "Vitality" , "Verve and dash" .)