Look, Tom’s admitted to cheating, OK? (4,2,8)
I believe the answer is:
fair to middling
'ok?' is the definition.
(I've seen this before)
'look tom's admitted to cheating' is the wordplay.
'look' becomes 'air' (I've seen this before).
'admitted to' means one lot of letters goes inside another.
'cheating' becomes 'fiddling' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'air'+'tom'='airtom'
'airtom' going into 'fiddling' is 'FAIR TO MIDDLING'.
Can you help me to learn more?
(Other definitions for fair to middling that I've seen before include "Not bad" , "Unremarkable" , "average" , "OK?" , "unexceptional" .)