Fictional millionaire, not straight, taking in bank (6)
I believe the answer is:
gatsby
'fictional millionaire' is the definition.
'gatsby' can be an answer for 'millionaire' (I have seen 'Novel millionaire' mean 'gatsby' so perhaps 'millionaire' could also mean 'gatsby'). I am not sure about the 'fictional' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for gatsby that I've seen before include "Fitzgerald's Great character" , "Famous novel by F Scott Fitzgerald 'The Great . . . . . .'" , "Novel millionaire" , "Jay, in books" , "Fitzgerald's great hero" .)