Talk at second summit (5)
I believe the answer is:
speak
'talk' is the definition.
(synonyms)
'at second summit' is the wordplay.
'at' is a charade indicator (letters next to each other).
'second' becomes 's' (common abbreviation).
'summit' becomes 'peak' (mountain peak).
's'+'peak' is 'SPEAK'.
(Other definitions for speak that I've seen before include "Utter words" , "express" , "give a lecture" , "Talk" , "Say something" .)