Warning doctor in front of Northern Ireland Conservative (8)
I believe the answer is:
monitory
'warning' is the definition.
('monitory' can be a synonym of 'warning')
'doctor in front of northern ireland conservative' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'in front of' means one lot of letters go next to another.
'northern ireland' becomes 'ni'.
'conservative' becomes 'tory' (I've seen this before).
'mo'+'ni'+'tory'='MONITORY'
(Other definitions for monitory that I've seen before include "Warning" , "Serving to warn - tiny room (anag)" .)