River bank home to beavers originally (5)
I believe the answer is:
tiber
'river' is the definition.
(I've seen this before)
'bank home to beavers originally' is the wordplay.
'bank' becomes 'tier' (both can mean a row of similar things).
'home to' is an insertion indicator (some letters house or home others).
'originally' suggests taking the first letters.
The first letter of 'beavers' is 'b'.
'tier' enclosing 'b' is 'TIBER'.
(Other definitions for tiber that I've seen before include "The flower of Rome" , "River entering the Mediterranean at Ostia" , "Roman river" , "Italian river with Ostia at its mouth" , "Italian banker" .)