Brighter Muslim meets the queen (7)
I believe the answer is:
'brighter' is the definition.
('sunny' can be similar in meaning to 'bright')
'muslim meets the queen' is the wordplay.
I cannot really see how this works, but
'muslim' could be 'sunni' (Sunni is an example) and 'sunni' is present in the answer.
'queen' could be 'er' (abbreviation for Elizabeth Regina) and 'er' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for sunnier that I've seen is " Better weather".)