Greek-Cypriot union is one's design (6)
I believe the answer is:
enosis
'greek-cypriot union' is the definition.
I can't judge whether this definition defines the answer.
'is one's design' is the wordplay.
'design' is an anagram indicator.
'is'+'ones'='isones'
'isones' is an anagram of 'ENOSIS'.
Can you help me to learn more?
(Other definitions for enosis that I've seen before include "Greek union" , "international union" , "Greek/Cypriot union" , "National union" , "goal in Cyprus once?" .)