Fit Soviet leader moving in (6)
I believe the answer is:
instal
'fit' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how one could define the other.
'soviet leader moving in' is the wordplay.
I cannot really see how this works, but
'in' is within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for instal that I've seen before include "Set up for use (anag.)" , "Give an office to" , "Place in position, ready for use" , "Set up ready for use" , "Place equipment in position" .)