History covers start of Moscow retreat (9)
I believe the answer is:
hermitage
'retreat' is the definition.
(I've seen this before)
'history covers start of moscow' is the wordplay.
'history' becomes 'heritage'.
'covers' means one lot of letters goes inside another.
'start of' says to take the initial letters.
The initial letter of 'moscow' is 'm'.
'heritage' enclosing 'm' is 'HERMITAGE'.
(Other definitions for hermitage that I've seen before include "St Petersburg museum - Rhone wine" , "art museum" , "Place of retreat" , "Secluded retreat" , "accommodation for one" .)