Upright vicar let off (8)
I believe the answer is:
vertical
'upright' is the definition.
(similar in meaning)
'vicar let off' is the wordplay.
'off' indicates an anagram.
'vicar'+'let'='vicarlet'
'vicarlet' with letters rearranged gives 'VERTICAL'.
(Other definitions for vertical that I've seen before include "At right angles to the horizontal" , "Absolutely upright" , "Ninety degrees to horizontal" , "At right angles to the base line" , "Perfectly upright" .)