Fool of doctor raises vermin in Ireland (8)
I believe the answer is:
imbecile
'fool' is the definition.
(I've seen this before)
'doctor raises vermin in ireland' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'raises' shows that the letters should be reversed in order.
'vermin' becomes 'lice' (I've seen this in another clue).
'in' indicates putting letters inside.
'ireland' becomes 'ie' (two letter country code).
'lice' in reverse letter order is 'ecil'.
'mb'+'ecil'='mbecil'
'mbecil' put inside 'ie' is 'IMBECILE'.
'of' is the link.
(Other definitions for imbecile that I've seen before include "A mentally deficient or stupid person" , "Jerk" , "Charlie" , "Numbskull" , "Abusive word for foolish person" .)