Fish set before the queen (7)
I believe the answer is:
grouper
'fish' is the definition.
(grouper is a kind of fish)
'set before the queen' is the wordplay.
I cannot quite understand how this works, but
'set' could be 'group' (group is a kind of set) and 'group' is found within the answer.
'queen' could be 'er' (short for Elizabeth Regina ie Queen Elizabeth) and 'er' is present in 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?
(Other definitions for grouper that I've seen before include "A fish" , "I order" , "that by implication isn't sole?" .)