Fellow diner's confusion, given herbal tea (8)
I believe the answer is:
messmate
'fellow diner's' is the definition.
(I've seen this before)
'confusion given herbal tea' is the wordplay.
'confusion' becomes 'mess' (mess can mean confusion or chaos).
'given' says to put letters next to each other.
'herbal tea' becomes 'mate' (South American hot drink. I am not sure about the 'herbal' bit.).
'mess'+'mate'='MESSMATE'
Can you help me to learn more?
(Other definitions for messmate that I've seen before include "He sits down with one" , "(In the navy) someone with whom one shares communal facilities" , "Sharer of the same (military) accommodation" , "Comrade in the services" , "Military colleague sharing a 4 down" .)