Eastern block united by Blake's last poem (7)
I believe the answer is:
eclogue
'last poem' is the definition.
'eclogue' can be an answer for 'poem' (I've seen this before). I'm not certain of the 'last' bit.
'eastern block united by blake's' is the wordplay.
'eastern' becomes 'e'.
'block' becomes 'clog' (clogging is a kind of blocking).
'united by blake' becomes 'ue' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'e'+'clog'+'ue'='ECLOGUE'
Can you help me to learn more?
(Other definitions for eclogue that I've seen before include "Work on farm" , "Bucolic" , "country-specific text" , "Poem about country" , "Short pastoral poem" .)