Out of this world Soviet jelly dipped in alcohol (7)
I believe the answer is:
gagarin
'out of this world soviet' is the definition.
(Yuri Gagarin, first human in space)
'jelly dipped in alcohol' is the wordplay.
'jelly' becomes 'agar' (gelatinous substance).
'dipped in' indicates putting letters inside.
'alcohol' becomes 'gin' (gin is a kind of alcohol).
'agar' inserted within 'gin' is 'GAGARIN'.
(Other definitions for gagarin that I've seen before include "Yuri --, cosmonaut" , "circumnavigator" , "Yuri --, space pioneer" , "Yuri ......, first Russian into space" , "old spaceman" .)