Put out an alert afterwards (5)
I believe the answer is:
later
'afterwards' is the definition.
(synonyms)
'put out an alert' is the wordplay.
'put out' is an anagram indicator.
'alert' with letters rearranged gives 'LATER'.
(Other definitions for later that I've seen before include "Not just yet" , "bye" , "Eventually" , "Following" , "Tardier" .)