Very enthusiastic man losing head (4)
I believe the answer is:
avid
'very enthusiastic' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for avid that I've seen before include "Keenly enthusiastic" , "Fervent" , "Eager like diva" , "Fanatical" , "'Eager, zealous (4)'" .)