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' says the answer is hidden in the clue.
'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" .)