Shown to wander in the outskirts of Preston (6)
I believe the answer is:
proven
'shown' is the definition.
(thesaurus)
'wander in the outskirts of preston' is the wordplay.
'wander' becomes 'rove' (synonyms).
'in the' indicates putting letters inside.
'outskirts of' says to hollow out the word (remove centre letters) (only letters on the outskirts).
'preston' with its centre removed is 'pn'.
'rove' placed into 'pn' is 'PROVEN'.
'to' acts as a link.
(Other definitions for proven that I've seen before include "Established with evidence" , "Conclusively demonstrated by evidence" , "Established beyond doubt" , "Adjective meaning demonstrated beyond doubt" .)