Celebration on the river-bank? (5)
I believe the answer is:
levee
'bank?' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for levee that I've seen before include "Embankment that should prevent flooding" , "Retaining embankment" , "Gathering" , "Morning reception once held by monarch" , "An embankment built to prevent a river from overflowing" .)