Queen of fish? (4)
I believe the answer is:
parr
This clue is a double definition.
'queen' is the first definition.
(Catherine Parr, sixth wife of Henry VIII)
'fish?' is the second definition.
(I know that parr is a type of young fish)
'of' acts as a link.
(Other definitions for parr that I've seen before include "Henry VIII's sixth queen" , "Wife surviving" , "Catherine ---, Henry VIII's widow" , "Young salmon or trout" , "Catherine --, Henry VIII's sixth wife" .)