Hieronymus perhaps swallowing king's soup (6)
I believe the answer is:
borsch
'soup' is the definition.
(I know that Borsch is a type of soup)
'hieronymus perhaps swallowing king's' is the wordplay.
'hieronymus perhaps' becomes 'Bosch' (15th-century artist Hieronymus Bosch).
'swallowing' is an insertion indicator.
'king' becomes 'R' (abbreviation of Latin rex).
'bosch' going around 'r' is 'BORSCH'.
(Other definitions for borsch that I've seen before include "Russian or Polish soup usually containing beet juice" , "Russian beetroot soup" , "Soup made with beetroot" .)