Space — it is awfully sterile (7)
I believe the answer is:
aseptic
'sterile' is the definition.
(synonyms)
'space it is awfully' is the wordplay.
'is awfully' is an anagram indicator.
'space'+'it'='spaceit'
'spaceit' anagrammed gives 'ASEPTIC'.
(Other definitions for aseptic that I've seen before include "Free from bacteria, surgically clean" , "avoiding germs" , "Free from bacteria, surically clean" , "Sterile" , "Paciest (anag.)" .)