An enormous number freely roll in it (8)
I believe the answer is:
trillion
'an enormous number' is the definition.
(I've seen this in another clue)
'freely roll in it' is the wordplay.
'freely' indicates an anagram.
'roll'+'in'+'it'='rollinit'
'rollinit' with letters rearranged gives 'TRILLION'.
(Other definitions for trillion that I've seen before include "One million million" , "1,000,000,000,000" , "US billion" , "A great number" , "Very large number" .)