Martial art demonstrated by artist seized by little Katherine (6)
I believe the answer is:
karate
'martial art' is the definition.
(I know that karate is a type of martial art)
'by artist seized by little katherine' is the wordplay.
'by' says to put letters next to each other.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'seized' means one lot of letters goes inside another.
'by' becomes 'ate' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'little' says to take the initial letters.
The initial letter of 'katherine' is 'k'.
'ra' put within 'ate' is 'arate'.
'arate' put after 'k' is 'KARATE'.
'demonstrated' is the link.
Can you help me to learn more?
(Other definitions for karate that I've seen before include "Jap. combat; sort of chop" , "Japanese martial art" , "Japanese form of unarmed combat" , "Unarmed-combat system" , "Japanese art of unarmed combat" .)