Family taking part (3)
I believe the answer is:
kin
'family' is the definition.
(I know that family can be written as kin)
'taking part' is the wordplay.
'part' indicates a hidden word.
'KIN' can be found hidden inside 'taking'.
(Other definitions for kin that I've seen before include "One's family/relations" , "A person's relatives, goes with kith" , "Connections; family" , "Flesh and blood" , "Relations, go with kith" .)