Sailor originally rowed into state by river (7)
I believe the answer is:
mariner
'sailor' is the definition.
(mariner is a kind of sailor)
'state by river' is the wordplay.
'state' becomes 'ma' (abbreviation for Massachusetts).
'by' becomes 'rine' (I can't explain this - if you can you should believe this answer much more).
'river' becomes 'r'.
'ma'+'rine'+'r'='MARINER'
'originally rowed into' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for mariner that I've seen before include "Sailor" , "Jack" , "Seafarer, old salt" , "Person sailing" , "Sea-goer, ancient in the poem" .)