Stray into outskirts of Killarney in Irish county (5)
I believe the answer is:
kerry
'irish county' is the definition.
(I've seen this before)
'stray into outskirts of killarney' is the wordplay.
'stray' becomes 'err' (synonyms).
'into' indicates putting letters inside.
'outskirts of' says to hollow out the word (remove centre letters).
'killarney' with its centre taken out is 'ky'.
'err' put inside 'ky' is 'KERRY'.
'in' is the link.
(Other definitions for kerry that I've seen before include "County of Ireland" , "Irish county" , "County < girl" , "County of Tralee" .)