Encourage rascal to get rid of posh Republican flag (5,5)

I believe the answer is:

jolly roger

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

'flag' is the definition.
(Jolly Roger is an example)

'encourage rascal to get rid of posh republican' is the wordplay.
'encourage' becomes 'jolly' (I can't justify this - if you can you should give a lot more credence to this answer).
'rascal' becomes 'rogue' (both can mean a scoundrel).
'to get rid of' suggests deleting specific letters.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'republican' becomes 'r' (abbreviation).
'rogue' with 'u' taken away is 'roge'.
'jolly'+'roge'+'r'='JOLLY ROGER'

Can you help me to learn more?

(Other definitions for jolly roger that I've seen before include "standard not welcomed in the main" , "standard for boarders?" , "Pirate flag" , "In the main a fearful sight" , "Pirates' flag" .)

I've seen this clue in The Telegraph.

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.