A little area containing zero flora and fauna (5)
I believe the answer is:
biota
'flora and fauna' is the definition.
(both can mean animal and plant life)
'a little area containing zero' is the wordplay.
'a little' becomes 'bit' (both can mean a small amount of something).
'area' becomes 'a' (maths abbreviation).
'containing' means one lot of letters goes inside another.
'zero' becomes 'O' (O resembles 0).
'bit'+'a'='bita'
'bita' going around 'o' is 'BIOTA'.
(Other definitions for biota that I've seen before include "Region's creatures, plants" , "Animal and plant life in an area" , "The animal and plant life of a region or period" .)