Strange argot comprehended by reliable proxy (9)
I believe the answer is:
surrogate
'proxy' is the definition.
(thesaurus)
'strange argot comprehended by reliable' is the wordplay.
I cannot really understand how this works, but
an anagram of 'argot' is 'rogat' which is present in the answer.
'reliable' could be 'sure' (similar in meaning) and 'sure' is present in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for surrogate that I've seen before include "One standing in" , "Deputising substitute" , "stand-in" , "(A) substitute in office" , "Argues about rot with substitute or deputy" .)