Europe perhaps happy restricting Northern Ireland, on reflection (9)
I believe the answer is:
continent
'europe perhaps' is the definition.
(Europe is a continent)
'happy restricting northern ireland on reflection' is the wordplay.
'happy' becomes 'content' (associated in meaning).
'restricting' indicates putting letters inside.
'northern ireland' becomes 'NI' (abbreviation).
'on reflection' is a reversal indicator.
'ni' in reverse letter order is 'in'.
'content' going around 'in' is 'CONTINENT'.
(Other definitions for continent that I've seen before include "dry?" , "Temperate - land mass" , "global sector" , "Africa, say" , "chaste" .)