Fervent, enthusiastic (6)
I believe the answer is:
ardent
This clue is a double definition.
'fervent' is the first definition.
(I know that fervent can be written as ardent)
'enthusiastic' is the second definition.
(similar in meaning)
(Other definitions for ardent that I've seen before include "Hot" , "Very keen" , "full of zeal" , "Passionate and glowing" , "Having great warmth of feeling like a lover" .)