Expedition at a distance, in small island (6)
I believe the answer is:
safari
'expedition' is the definition.
(I know that safari is a type of expedition)
'a distance in small island' is the wordplay.
'a distance' becomes 'afar' (from afar).
'in' indicates putting letters inside.
'small' becomes 's' (abbreviation - e.g. clothes size).
'island' becomes 'i' (geographical abbreviation).
's'+'i'='si'
'afar' going into 'si' is 'SAFARI'.
'at' is the link.
(Other definitions for safari that I've seen before include "Trip to see wild animals" , "North African capital" , "Hunting expedition (in Africa)" , "Hunting journey" , "Overland journey by hunters" .)