Obscure English Tories upset with Commons at first (8)
I believe the answer is:
Here is my best explanation:
'obscure' is the definition.
'english tories upset with commons at first' is the subsidiary indication.
'english' becomes 'e' (abbreviation).
'upset' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'at first' says to take the initial letters.
The first letter of 'commons' is 'c'.
'tories' anagrammed gives 'soteri'.
(Other definitions for esoteric that I've seen before include "Abstruse, obscure", "Mysterious to all but a chosen few", "Understood by only a few people", "Coteries (anag.)", "Obscure, abstruse", "Tie score (anagram)", "Intelligible only to the initiated", "Secret; taught to few", "I set core up to be mysterious" and "Secret, mysterious".)