PM over in Irish county (4)
I believe the answer is:
mayo
'irish county' is the definition.
(county in Ireland)
'pm over' is the wordplay.
'pm' becomes 'May' (former UK prime minister Theresa May).
'over' becomes 'o' (cricket abbreviation).
'may'+'o'='MAYO'
'in' is the link.
(Other definitions for mayo that I've seen before include "part of Ireland" , "radio presenter" , "County of north-west Ireland" , "Irish county; dressing" , "Ir. county; salad dressing" .)