Assemble at meeting (5)
I believe the answer is:
rally
I believe this clue is a double definition.
'assemble' is the first definition.
(thesaurus)
'meeting' is the second definition.
(I have seen 'Mass meeting ' mean 'rally' so perhaps 'meeting' could also mean 'rally')
'at' acts as a link.
(Other definitions for rally that I've seen before include "Large gathering" , "(Of shares) increase after a fall" , "Arouse for action" , "Recover; mass meeting" , "Exchange of shots (tennis)" .)