Look down on river holding drinks up (7)
I believe the answer is:
despise
'look down on' is the definition.
(synonyms)
'river holding drinks up' is the wordplay.
'river' becomes 'dee' (River Dee).
'holding' indicates putting letters inside.
'drinks' becomes 'sips' (sipping is a kind of drinking).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'sips' written backwards gives 'spis'.
'dee' placed around 'spis' is 'DESPISE'.
(Other definitions for despise that I've seen before include "Scorn; loathe" , "Look down upon" , "Abhor" , "Feel contempt for; scorn" , "Look down on with disdain" .)