Legal opinions in old rambling diatribe enthralling court (6,5)
I believe the answer is:
obiter dicta
'legal opinions' is the definition.
'obiter dicta' can be an answer for 'opinions' (obiter dictum is a kind of opinion). I'm not sure about the 'legal' bit.
'old rambling diatribe enthralling court' is the wordplay.
I cannot quite understand how this works, but
'old' could be 'o' (abbreviation as in OT - Old Testament) and 'o' is present in the answer.
'court' could be 'ct' (abbreviation used in road names) and 'ct' is found in the answer.
an anagram of 'diatribe' is 'biterdia' which is within the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for obiter dicta that I've seen before include "passing remarks" , "comments from the judge - with 7d" , "Incidental remarks by judge" , "Departures" , "Mentions" .)