Graphical record of one small cat amid upset horses (10)
I believe the answer is:
'graphical record' is the definition.
(I know that seismogram is a type of graphical record)
'one small cat amid upset horses' is the wordplay.
'one' becomes 'I' (Roman numeral).
'small cat' becomes 'smog' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'amid' means one lot of letters goes inside another.
'upset' says the letters should be written backwards.
'horses' becomes 'mares' (female horses).
'mares' backwards is 'seram'.
'ismog' placed inside 'seram' is 'SEISMOGRAM'.
'of' acts as a link.
Can you help me to learn more?
(Another definition for seismogram that I've seen is " Record of quivering".)