Upright canons hit out (9)
I believe the answer is:
stanchion
'upright' is the definition.
(I've seen this before)
'canons hit out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'canons'+'hit'='canonshit'
'canonshit' is an anagram of 'STANCHION'.
(Other definitions for stanchion that I've seen before include "Vertical post or rod as a support" , "Post or rod used as a support" , "Upright" .)