Foolish king put outside home in a row (6)
I believe the answer is:
linear
'in a row' is the definition.
'foolish king put outside home' is the wordplay.
'foolish king' becomes 'lear' (reference to King Lear).
'put outside' means one lot of letters goes inside another.
'home' becomes 'in' ('he's home' can mean 'he's in').
'lear' placed around 'in' is 'LINEAR'.
(Other definitions for linear that I've seen before include "One-dimensional" , "Of a line or length" , "In a straight line" , "Like some ancient scripts" , "Long and narrow, of one dimension" .)