Trendy river horse at the river (5)
I believe the answer is:
hippo
'horse at the river' is the definition.
I can't tell whether this defines the answer.
'trendy river' is the wordplay.
'trendy' becomes 'hip' (both can mean fashionable).
'river' becomes 'Po' (Italian river).
'hip'+'po'='HIPPO'
Can you help me to learn more?
(Other definitions for hippo that I've seen before include "One thick-skinned" , "Afr. river mammal" , "one that's large and fleshy" , "Mammoth African mammal (abbr)" , "African animal (shortened)" .)