He again is with us (4)
I believe the answer is:
here
'with us' is the definition.
(I've seen this in another clue)
'he again' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'he'+'re'='HERE'
'is' acts as a link.
(Other definitions for here that I've seen before include "Present; I say!" , "Present - at this point" , "The present location" , "On this spot" , "In this place - present" .)