I got mixed up with Rachel - I'm an idiot (7)
I believe the answer is:
charlie
'i'm an idiot' is the definition.
I can't tell whether this defines the answer.
'i got mixed up with rachel' is the wordplay.
'got mixed up with' is an anagram indicator.
'i' anagrammed with 'rachel' gives 'CHARLIE'.
Can you help me to learn more?
(Other definitions for charlie that I've seen before include "Comms code C" , "Code word for letter C" , "Chaplinesque man" , "Silly person" , "dope > (cocaine)" .)