Beast with a waterside joint (5)
I believe the answer is:
hippo
'beast' is the definition.
(I've seen this before)
'a waterside joint' is the wordplay.
I cannot quite understand how this works, but
'joint' could be 'hip' (hip is a kind of joint) and 'hip' is found within the answer.
The remaining letters 'po' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'with' acts as a link.
Can you help me to learn more?
(Other definitions for hippo that I've seen before include "Tropical African mud wallower" , "Large semi-aquatic mammal (abbr)" , "Wallowing mammal" , "One thick-skinned" , "African river mammal" .)