Weapon deposited in river, alas (4,2)
I believe the answer is:
dear me
'alas' is the definition.
I know nothing about this answer so I can't tell whether this works.
'weapon deposited in river' is the wordplay.
'weapon' becomes 'arm' (I've seen this before).
'deposited in' indicates putting letters inside.
'river' becomes 'dee' (River Dee).
'arm' put into 'dee' is 'DEAR ME'.
Can you help me to learn more?
(Other definitions for dear me that I've seen before include "Mild expression of distress from expensive self" , "Expression of dismay" , "Expression of mild regret from precious self" , "how sad" , "What a pity" .)