Room 101 's about coverage of Poles (7)
I believe the answer is:
icecaps
'coverage of poles' is the definition.
(coverage of the Earth's poles)
'room 101 's about' is the subsidiary indication.
'room' becomes 'space' (I've seen this before**).
's0s ' becomes 'ci'.
'about' says the letters should be written backwards.
'space'+'ci'='spaceci'
'spaceci' backwards is 'icecaps'.
(Other definitions for icecaps that I've seen before include "Glacial areas" , "Areas of permanent glaciation" , "They cover Poles" , "Cold headgear, perhaps?" , "White sheets" .)