The Sun, for one, may be a bit loud and non-U (7)
I believe the answer is:
tabloid
'the sun' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'one may be a bit loud and non-u' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'a' is present in the answer.
'bit' could be 'o' (resembles 0, a binary digit or bit) and 'o' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'for' acts as a link.
Can you help me to learn more?
(Other definitions for tabloid that I've seen before include "Newspaper with smaller pages and popular content" , "Type of newspaper" , "Ad lib to get lowbrow newspaper" , "Popular newspaper size" , "Not our sort of paper" .)