Splurge on holiday at river's edge (5,3,4)
I believe the answer is:
break the bank
'splurge' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'on holiday at river's edge' is the wordplay.
'on' says to put letters next to each other.
'holiday' becomes 'break' (break can mean a holiday or time off).
'at' becomes 'the' (I can't justify this - if you can you should believe this answer much more).
'river's edge' becomes 'bank' (I've seen this before).
'break'+'the' is 'breakthe'.
'breakthe'+'bank'='BREAK THE BANK'
Can you help me to learn more?
(Other definitions for break the bank that I've seen before include "Spend on something more than one can afford" , "Ruin the riverside" , "current expansion may" , "Make a mint" , "Win casino's maximum" .)