Expand Caribbean retreat (5)
I believe the answer is:
widen
'expand' is the definition.
(I've seen this before)
'caribbean retreat' is the wordplay.
'caribbean' becomes 'WI' (abbreviation for the West Indies).
'retreat' becomes 'den' (both can mean a lair or hideout).
'wi'+'den'='WIDEN'
(Other definitions for widen that I've seen before include "Make broader" , "Dilate" , "Spread" , "Stretch sideways" , "Broaden - enlarge" .)