To keep small, company dismisses Ukrainians, perhaps (8)
I believe the answer is:
cossacks
'ukrainians perhaps' is the definition.
(the Cossack people originated in Ukraine)
'to keep small company dismisses' is the wordplay.
'to keep' means one lot of letters goes inside another.
'small' becomes 's' (abbreviation - e.g. clothes size).
'company' becomes 'co' (abbreviation).
'dismisses' becomes 'sacks' ('sack' can be a synonym of 'dismiss').
'co'+'sacks'='cosacks'
's' going into 'cosacks' is 'COSSACKS'.
(Other definitions for cossacks that I've seen before include "Members of an elite cavalry corps in tsarist Russia" , "Russian peasants?" , "Famous horsemen of S Russia" .)