What once involved two banks in a row? (6)
I believe the answer is:
bireme
'row?' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for bireme that I've seen before include "Ancient galley with two banks of oars on each side" , "Ancient rowed warship" , "old vessel?" , "Rowed boat long ago" , "rowing boat" .)