One driven mad by Regan and ilk? (4,4)
I believe the answer is:
king lear
'one' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'driven mad by regan and ilk?' is the wordplay.
'driven mad by' indicates an anagram.
'and' is a charade indicator (letters next to each other).
'regan'+'ilk'='reganilk'
'reganilk' is an anagram of 'KING LEAR'.
Can you help me to learn more?
(Other definitions for king lear that I've seen before include "One of Shakespeare's tragedies" , "drama" , "Shakespeare's foolish tragic monarch" , "Shakespeare play with storm scene" , "Part of ruler" .)