Horse in box pursued by crazy character (8)
I believe the answer is:
chestnut
'horse' is the definition.
(chestnut is a kind of horse)
'in box pursued by crazy character' is the wordplay.
'in' means one lot of letters goes inside another.
'box pursued by' becomes 'cest' (I am not sure about this - if you are sure you should believe this answer much more).
'crazy' becomes 'nut' (I've seen this before).
'character' becomes 'h'.
'cest'+'nut'='cestnut'
'cestnut' enclosing 'h' is 'CHESTNUT'.
Can you help me to learn more?
(Other definitions for chestnut that I've seen before include "Wood" , "Brown horse" , "Hunt sect behind a big tree" , "comedian's overused line?" , "Dark golden-brown horse" .)