Lots of data about slight Southern squalor (10)
I believe the answer is:
filthiness
'squalor' is the definition.
(I've seen this before)
'lots of data about slight southern' is the wordplay.
'lots of data' becomes 'files' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'about' is an insertion indicator.
'slight' becomes 'thin' (similar in meaning).
'southern' becomes 's' (abbreviation).
'files' placed around 'thin' is 'filthines'.
'filthines'+'s'='FILTHINESS'
Can you help me to learn more?
(Another definition for filthiness that I've seen is " Squalor".)