Coffee reps angered by Standard Oil (8)
I believe the answer is:
espresso
'coffee' is the definition.
(espresso is a kind of coffee)
'reps angered by standard oil' is the wordplay.
I cannot quite see how this works, but
an anagram of 'reps' is 'espr' which is located in the answer.
The remaining letters 'esso' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for espresso that I've seen before include "Italian strong coffee traditionally in a little cup" , "Strong coffee made with steam machine" , "that's stimulating" , "Kind of shot" , "It's made by forcing steam through ground coffee beans" .)