Technical word island country used for “ending” (11)
I believe the answer is:
termination
'ending' is the definition.
(termination is a kind of ending)
'technical word island country' is the wordplay.
'technical word' becomes 'term'.
'island' becomes 'i'.
'country' becomes 'nation' ('nation' can be a synonym of 'country').
'term'+'i'+'nation'='TERMINATION'
'used for' is the link.
(Other definitions for termination that I've seen before include "End" , "An ending" , "Conclusion" , "Stopping" , "Finish" .)