Standing up, let vicar out (8)
I believe the answer is:
vertical
'standing up' is the definition.
(thesaurus)
'let vicar out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'let'+'vicar'='letvicar'
'letvicar' anagrammed gives 'VERTICAL'.
(Other definitions for vertical that I've seen before include "Not laid down" , "Upright, perpendicular" , "Absolutely upright" , "Perfectly upright" , "At right angles to the horizontal" .)