Thrash king hiding article (7)
I believe the answer is:
leather
'thrash' is the definition.
(to hit or thrash with leather)
'king hiding article' is the wordplay.
'king' becomes 'lear' (Shakespeare's King Lear).
'hiding' means one lot of letters goes inside another.
'article' becomes 'the' (the definite article in English).
'lear' going around 'the' is 'LEATHER'.
(Other definitions for leather that I've seen before include "kid, perhaps" , "kid, say" , "Polishing cloth" , "durable material" , "polish" .)