Beside oneself (7)
'beside oneself' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for frantic that I've seen before include "At the end of one's tether" , "Mad" , "'Unrestrained, overly agitated (7)'" , "Distraught with fear" , "Excessively agitated" .)
(Other definitions for excited that I've seen before include "in high spirits" , "Aroused, enthused" , "in agitated state" , "Hot" , "Feeling a pleasant tension" .)
(Other definitions for fuming that I've seen before include "Showing anger, really hot" , "Smoking with rage" , "getting cross" , "Smoking (with anger?)" , "Livid" .)