Real party island (8)
I believe the answer is:
concrete
'real' is the definition.
(similar in meaning)
'party island' is the wordplay.
'party' becomes 'con' (abbreviation for Conservative Party).
'island' becomes 'crete' (Greek island).
'con'+'crete'='CONCRETE'
(Other definitions for concrete that I've seen before include "that may be reinforced" , "Specific - building material" , "setter" , "Specific; definite" , "Real, not abstract" .)