Brighten up space, as it happens, by noon (7)
I believe the answer is:
enliven
'brighten up' is the definition.
(I've seen this before)
'space as it happens by noon' is the wordplay.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'as it happens' becomes 'live' (as in live broadcasting).
'by' means one lot of letters go next to another.
'noon' becomes 'n' (abbreviation).
'en'+'live'+'n'='ENLIVEN'
(Other definitions for enliven that I've seen before include "Put zip or vim into" , "Pep up" , "Inject vim into, energise" , "Excite" , "Wake" .)