Russian writer's play excited lots inside (7)
I believe the answer is:
tolstoy
'russian writer's' is the definition.
(I've seen this before)
'play excited lots inside' is the wordplay.
'play' becomes 'toy' ('toy' can be a synonym of 'play').
'excited' indicates anagramming the letters.
'inside' indicates putting letters inside.
'lots' anagrammed gives 'olst'.
'toy' placed around 'olst' is 'TOLSTOY'.
(Other definitions for tolstoy that I've seen before include "Writer of War and Peace, d.1910" , "Russian novelist" , "Great Russian author of 'War and Peace'" , "Count Leo . . . . . . . wrote 'War and Peace'" , "Russian writer, 1828-1910" .)