Wild donkey that's lost its tail in the fencing (5)
I believe the answer is:
kendo
'the fencing' is the definition.
(I've seen this before)
'wild donkey that's lost its tail' is the wordplay.
I cannot quite understand how this works, but
'tail' could be 'end' (the tail of something can mean the end) and 'end' is present in the answer.
The remaining letters 'ko' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for kendo that I've seen before include "Japanese martial art using split bamboo swords" , "discipline" , "Combat" , "Japanese art of fencing with staves" , "wooden fencing?" .)