Run down giant deer in confusion (9)
I believe the answer is:
denigrate
'run down' is the definition.
(I've seen this before)
'giant deer in confusion' is the wordplay.
'in confusion' is an anagram indicator.
'giant'+'deer'='giantdeer'
'giantdeer' is an anagram of 'DENIGRATE'.
(Other definitions for denigrate that I've seen before include "Disparage" , "Unfairly criticise" , "Run down" , "Criticise, belittle" , "Bad-mouth" .)