President's earlier a failing, ungrateful character (5)

I believe the answer is:

regan

I'm a little stuck... Click here to teach me more about this clue!

'failing ungrateful character' is the definition.
The definition suggests a singular noun which matches the answer.

'president's earlier a' is the wordplay.
'president's earlier' becomes 'reg' (I can't explain this - if you can you should believe this answer much more).
'a' becomes 'an'.
'reg'+'an'='REGAN'

Can you help me to learn more?

(Other definitions for regan that I've seen before include "Possessed gir" , "role at Stratford" , "Princess" , "part of 1 25 [KING LEAR]" , "better half of Cornwall" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.