The fellow gets about — but not there (4)
I believe the answer is:
here
'not there' is the definition.
('here' is the opposite to 'there')
'the fellow gets about' is the wordplay.
'the fellow' becomes 'he' (I've seen this in other clues).
'gets' says to put letters next to each other.
'about' becomes 're' (regarding**).
'he'+'re'='HERE'
'but' is the link.
(Other definitions for here that I've seen before include "In attendance" , "At this stage" , "Hither" , "To hand" , "On this spot" .)