Muster (6)
'muster' is the definition.
(I know that muster is a more specific form of gather)
This is all the clue.
(Other definitions for gather that I've seen before include "Bring or assemble together" , "Collect or asemble" , "Collect or assemble" , "Convene" , "Congregate" .)
'muster' is the definition.
(thesaurus)
This is the entire clue.
(Another definition for round-up that I've seen is " Summary of events".)