Composer’s Shakespearean king eclipsing Henry (5)
I believe the answer is:
lehar
'composer's' is the definition.
(Austro-Hungarian composer Franz Lehar)
'shakespearean king eclipsing henry' is the wordplay.
'shakespearean king' becomes 'lear' (King Lear).
'eclipsing' is an insertion indicator (to eclipse can mean to cover up or hide).
'henry' becomes 'h' (symbol for the unit of electrical inductance).
'lear' going around 'h' is 'LEHAR'.
(Other definitions for lehar that I've seen before include "He scored" , "Austrian of note" , "Viennese composer" , "Hungarian who composed" , "Franz . . . . . composed 'The Merry Widow'" .)