The fellow sitting on road in a crowd (4)
I believe the answer is:
herd
'a crowd' is the definition.
(I've seen this before)
'the fellow sitting on road' is the wordplay.
'the fellow' becomes 'he' (I've seen this in other clues).
'sitting on' means one lot of letters go next to another.
'road' becomes 'rd' (abbreviation).
'he'+'rd'='HERD'
'in' acts as a link.
(Other definitions for herd that I've seen before include "Collection of swine" , "Large group of animals" , "Stock of cattle" , "Host" , "Group of cows, elephants etc" .)