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' means to remove the middle letters (only letters on the outskirts).
'preston' with its centre taken out is 'pn'.
'rove' placed inside 'pn' is 'PROVEN'.
'to' is the 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" .)