Strangers travelling south go too far (10)
I believe the answer is:
transgress
'go too far' is the definition.
(thesaurus)
'strangers travelling south' is the wordplay.
'travelling' indicates anagramming the letters.
'south' becomes 's' (abbreviation).
'strangers' anagrammed gives 'transgres'.
'transgres'+'s'='TRANSGRESS'
(Other definitions for transgress that I've seen before include "Go beyond (legal) limits" , "Commit a sin" , "Cause offence" , "Break (limit, law)" , "commit offence" .)