Islamist Queen of more cheerful disposition (7)

I believe the answer is:

sunnier

'of more cheerful disposition' is the definition.
(sunny can mean cheerful)

'islamist queen' is the wordplay.
'islamist' becomes 'Sunni' (as in Sunni Islam).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'sunni'+'er'='SUNNIER'

(Another definition for sunnier that I've seen is " Better weather".)

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.