Boxer consumes cabbage endlessly in compound (6)
I believe the answer is:
alkali
'compound' is the definition.
(alkali is a kind of compound)
'boxer consumes cabbage endlessly' is the wordplay.
'boxer' becomes 'Ali' (Muhammad Ali).
'consumes' means one lot of letters goes inside another.
'cabbage endlessly' becomes 'kal' (I can't justify this - if you can you should give a lot more credence to this answer).
'ali' going around 'kal' is 'ALKALI'.
'in' is the link.
Can you help me to learn more?
(Other definitions for alkali that I've seen before include "Eg, lime or caustic soda" , "Compound like lime" , "Substance with pH of over 7" , "Acid neutraliser" , "Substance turning litmus paper blue" .)