Melanie has style and vigour (4)
I believe the answer is:
elan
'style and vigour' is the definition.
(I've seen this before)
'melanie has' is the wordplay.
'has' indicates a hidden word.
'ELAN' is hidden within 'melanie'.
(Other definitions for elan that I've seen before include "Dash in French lane" , "Impetuosity - style" , "Vivacity, panache" , "Dash and enthusiasm." , "Vigour, style, enthusiasm" .)