Flood at lower level around river (5)
I believe the answer is:
drown
'flood' is the definition.
(I've seen this before)
'lower level around river' is the wordplay.
'lower level' becomes 'down' (I can't justify this - if you can you should give a lot more credence to this answer).
'around' is an insertion indicator.
'river' becomes 'r' (abbreviation for river).
'down' going around 'r' is 'DROWN'.
'at' acts as a link.
Can you help me to learn more?
(Other definitions for drown that I've seen before include "Die in sea" , "Kill by submersion" , "Immerse (fatally?)" , "Die from submersion in liquid" , "Become submerged" .)