Peril Cuba largely represented as one of USSR's vassals (8)
I believe the answer is:
republic
'one of ussr's vassals' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'peril cuba largely represented' is the wordplay.
'largely' means to remove the last letter (most but not all of the letters).
'represented' is an anagram indicator.
'peril'+'cuba'='perilcuba'
'perilcuba' with its final letter taken away is 'perilcub'.
'perilcub' is an anagram of 'REPUBLIC'.
'as' acts as a link.
Can you help me to learn more?
(Other definitions for republic that I've seen before include "Commonwealth" , "The political system is an epic blur" , "Political system of government by the people" , "Non-monarchical state" , "State without monarch" .)