Stood up to return coffee lacking something essential (5)
I believe the answer is:
decaf
'coffee lacking something essential' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'stood up to return' is the wordplay.
'stood up to' becomes 'faced' (face can mean to confront or stand up to).
'return' is a reversal indicator.
'faced' back-to-front is 'DECAF'.
Can you help me to learn more?
(Other definitions for decaf that I've seen before include "Cup substitute missing kick" , "Type of coffee" , "Non-alcoholic drink" , "Less stimulating coffee?" , "Coffee without the kick?" .)