Changes One put out by East European composer (6)
I believe the answer is:
varese
'composer' is the definition.
(I've seen this before)
'changes one put out by east european' is the wordplay.
'changes' becomes 'varies' ('vary' can be a synonym of 'change').
'one' becomes 'i' (Roman numeral).
'put out by' suggests deleting specific letters.
'east european' becomes 'e' (abbreviation e.g. EU. I am not sure about the 'east' bit.).
'varies' with 'i' removed is 'vares'.
'vares'+'e'='VARESE'
Can you help me to learn more?
(Other definitions for varese that I've seen before include "European compser" , "Dissonant composer" , "Italian city" , "Edgar --, composer" .)