What the average fan does removes uncertainty (6,3,3)
I believe the answer is:
clears the air
'what the average fan' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'removes uncertainty' is the wordplay.
'removes' becomes 'clears' (clearing is a kind of removing).
'uncertainty' becomes 'theair' (I can't justify this - if you can you should give a lot more credence to this answer).
'clears'+'theair'='CLEARS THE AIR'
'does' is the link.
Can you help me to learn more?
(Another definition for clears the air that I've seen is " Defuses a tense situation by talking frankly".)