Gather in from the terminus, possibly (6)
I believe the answer is:
muster
'gather' is the definition.
(mustering is a kind of gathering)
'in from the terminus possibly' is the wordplay.
'from' suggests deleting specific letters.
'possibly' indicates anagramming the letters.
'terminus' with 'in' taken away is 'termus'.
'termus' is an anagram of 'MUSTER'.
(Other definitions for muster that I've seen before include "marshal" , "a lot of peacocks" , "Mobilize" , "Assemble, gather together" , "Assemble for duty" .)