Greek island dispenses with old Russian people (8)
I believe the answer is:
cossacks
'old russian people' is the definition.
I know nothing about this answer so I can't tell whether this works.
'greek island dispenses' is the wordplay.
'greek island' becomes 'cos' (I've seen this before).
'dispenses' becomes 'sacks' (I can't justify this - if you can you should believe this answer much more).
'cos'+'sacks'='COSSACKS'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for cossacks that I've seen before include "Members of an elite cavalry corps in tsarist Russia" , "Famous horsemen of S Russia" , "Russian peasants?" .)