Treatment on one kid almost finished (5)
I believe the answer is:
reiki
'treatment' is the definition.
I know nothing about this answer so I can't tell whether this works.
'on one kid almost finished' is the wordplay.
'on' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'almost' means to remove the last letter (almost the whole word is kept).
'finished' becomes 're' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'i'+'kid'='ikid'
'ikid' with its final letter taken off is 'iki'.
'iki' after 're' is 'REIKI'.
Can you help me to learn more?
(Other definitions for reiki that I've seen before include "Japanese massage" , "Hands-on treatment" , "therapy" , "Energy-channelling healing technique" , "Energy healing technique" .)