Black bird died in flock (5)
I believe the answer is:
crowd
'flock' is the definition.
(thesaurus)
'black bird died' is the wordplay.
'black bird' becomes 'crow' (I've seen this before).
'died' becomes 'd'.
'crow'+'d'='CROWD'
'in' acts as a link.
(Other definitions for crowd that I've seen before include "Large number of people in one place" , "Spectators" , "Large number of people gathered together" , "Multitude" , "Army" .)