Hawking scam on river and railway (8)
I believe the answer is:
falconry
'hawking' is the definition.
(thesaurus)
'scam on river and railway' is the wordplay.
'scam' becomes 'con' (I've seen this before).
'on' means one lot of letters go next to another.
'river' becomes 'fal' (I've seen this before**).
'and' says to put letters next to each other.
'railway' becomes 'ry' (abbreviation for railway).
'con' after 'fal' is 'falcon'.
'falcon'+'ry'='FALCONRY'
(Other definitions for falconry that I've seen before include "Keeping of birds of prey" , "art of hunting with certain birds of prey" , "Sport" .)