Mother has nothing for Chinese chairman (3)
I believe the answer is:
mao
'chinese chairman' is the definition.
(I've seen this before)
'mother has nothing' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'has' says to put letters next to each other.
'nothing' becomes 'O' (looks like zero - 0).
'ma'+'o'='MAO'
'for' is the link.
(Other definitions for mao that I've seen before include "Former Chinese leader" , "Old Chinese "Chairman"" , "The familiar Tse-Tung" , "Chinese leader (d.nineteen seventy six)" , "Great Chinese leader . . . Tse-Tung (3)" .)