Clean space, it being messy (7)
I believe the answer is:
aseptic
'clean' is the definition.
(I've seen this before)
'space it being messy' is the wordplay.
'being messy' indicates anagramming the letters.
'space'+'it'='spaceit'
'spaceit' is an anagram of 'ASEPTIC'.
(Other definitions for aseptic that I've seen before include "Free from harmful bacteria" , "avoiding germs" , "Sterile" , "Spicate (anag.)" , "Free of bacterial or viral contamination" .)