Gather in from the terminus, possibly (6)
I believe the answer is:
muster
'gather' is the definition.
(I know that muster is a type of gather)
'in from the terminus possibly' is the wordplay.
'from' is a deletion indicator.
'possibly' indicates anagramming the letters.
'terminus' with 'in' taken away is 'termus'.
'termus' with letters rearranged gives 'MUSTER'.
(Other definitions for muster that I've seen before include "marshal" , "a lot of peacocks" , "Mobilize" , "Assemble, gather together" , "Assemble for duty" .)