One's little room covered in a lot of jumble (10)
I believe the answer is:
miscellany
'jumble' is the definition.
(thesaurus)
'one's little room covered in a lot' is the wordplay.
'one's' becomes 'i's' (Roman numeral).
'little room' becomes 'cell' (I've seen this before).
'covered in' means one lot of letters goes inside another.
'a lot' becomes 'many' (many means a lot).
'is'+'cell'='iscell'
'iscell' placed within 'many' is 'MISCELLANY'.
'of' acts as a link.
(Other definitions for miscellany that I've seen before include "motley group?" , "Hotch-potch" , "varied group" , "authors contribute" , "anthology" .)