Translator's boy held up by river in the north-east (7)

'translator's' is the definition.
(I know that Tyndale is a translators)

'boy held up by river in the north-east' is the wordplay.
'boy' becomes 'lad' (informal term for boy).
'held up by' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'river in' becomes 'nyt' (I can't justify this - if you can you should believe this answer much more).
'the north' says the letters should be written backwards (in a down clue, letters go up or 'northward').
'east' becomes 'e' (abbreviation).
'lad'+'nyt'='ladnyt'
'ladnyt' backwards is 'tyndal'.
'tyndal'+'e'='TYNDALE'

Can you help me to learn more?