A great mist swirled around one on bench? (10)
I believe the answer is:
magistrate
'one on bench?' is the definition.
(I've seen this before)
'a great mist swirled' is the wordplay.
'swirled' indicates an anagram.
'a'+'great'+'mist'='agreatmist'
'agreatmist' with letters rearranged gives 'MAGISTRATE'.
'around' acts as a link.
(Other definitions for magistrate that I've seen before include "Person in court" , "Dispenser of justice" , "JP" , "Capital of Ethiopia" , "Judge" .)