He's on the road with a group (4)
I believe the answer is:
herd
'group' is the definition.
(a herd is a group or pack)
'he's on the road' is the wordplay.
'on' says to put letters next to each other (in a down clue, letters appear on others).
'the road' becomes 'rd' (abbreviation).
'he'+'rd'='HERD'
'with a' is the link.
(Other definitions for herd that I've seen before include "The rabble" , "Group of animals, cattle, say" , "Group of cows, elephants etc" , "Collection of cattle" , "Flock" .)