Japanese currency backed in memo somehow seen by northern financiers (8)

'northern financiers' is the definition.
'moneymen' can be an answer for 'financiers' (I've seen this before). I'm not sure about the 'northern' bit.

'japanese currency backed in memo somehow seen' is the wordplay.
'japanese currency' becomes 'yen' (I've seen this before).
'backed' shows that the letters should be reversed in order.
'in' is an insertion indicator.
'somehow' is an anagram indicator.
'seen' becomes 'n' (I can't justify this - if you can you should give a lot more credence to this answer).
'yen' back-to-front is 'ney'.
'memo' with letters rearranged gives 'mome'.
'ney' inserted inside 'mome' is 'moneyme'.
'moneyme'+'n'='MONEYMEN'

'by' is the link.