Man taking part, showing enthusiasm (4)
I believe the answer is:
gent
'man' is the definition.
(gent is a kind of man)
'part showing enthusiasm' is the wordplay.
'part' indicates a hidden word.
'GENT' can be found hidden inside 'showing enthusiasm'.
'taking' is the link.
(Other definitions for gent that I've seen before include "Auctioneer's tool" , "bloke" , "Chap, fellow" , "cove" , "Informal and short man" .)