Balloon, something round and white (8)
I believe the answer is:
'balloon' is the definition.
'round and white' is the wordplay.
'round' becomes 'ball' (I've seen this before).
'and' means one lot of letters go next to another.
'white' becomes 'snow' (I can't explain this - if you can you should give a lot more credence to this answer).
'ball' put after 'snow' is 'SNOWBALL'.
'something' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for snowball that I've seen before include "Wintry missile - demonised by 17" , "Cocktail made from lemonade and advocaat" , "Advocaat cocktail - escalate" , "Throw it in winter" , "Increase rapidly in size - advocaat and lemonade" .)