Safe to cross English border in the outskirts (9)
I believe the answer is:
perimeter
'the outskirts' is the definition.
(thesaurus)
'safe to cross english border' is the wordplay.
'safe' becomes 'peter' (I've seen this before).
'to cross' indicates putting letters inside.
'english' becomes 'e' (abbreviation).
'border' becomes 'rim' (I've seen this before**).
'e'+'rim'='erim'
'peter' going around 'erim' is 'PERIMETER'.
'in' is the link.
(Other definitions for perimeter that I've seen before include "Enclosing boundary" , "Exterior of a plane figure" , "bounds" , "Outer boundary" , "Prime tree (anag.)" .)