Judge turned to note (3)
I believe the answer is:
jot
'note' is the definition.
(jot is a kind of note)
'judge turned to' is the wordplay.
'judge' becomes 'j'.
'turned' says the letters should be written in reverse.
'to' reversed gives 'ot'.
'j'+'ot'='JOT'
(Other definitions for jot that I've seen before include "Set down briefly" , "Small piece - note" , "Scrap" , "Write a short note" , "Write hastily - a very small amount" .)