Do they keep rooms cool and bright? (9)
I believe the answer is:
fanlights
'do they keep rooms' is the definition.
The definition suggests an adverb but the answer is not.
'cool and bright?' is the wordplay.
'cool' becomes 'fan' (I've seen this before).
'and' means one lot of letters go next to another.
'bright?' becomes 'lights' (I can't justify this - if you can you should believe this answer much more).
'fan'+'lights'='FANLIGHTS'
Can you help me to learn more?
(Other definitions for fanlights that I've seen before include "Windows" , "They cap entries" .)