Miniature basin broken: nothing in that (6)
I believe the answer is:
bonsai
'miniature' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'basin broken nothing in that' is the wordplay.
'broken' indicates anagramming the letters.
'nothing' becomes 'O' (looks like zero - 0).
'in that' means one lot of letters goes inside another.
'basin' anagrammed gives 'bnsai'.
'bnsai' placed around 'o' is 'BONSAI'.
Can you help me to learn more?
(Other definitions for bonsai that I've seen before include "Potted tree or shrub artificially prevented from reaching normal size" , "Japanese craft of growing miniature trees" , "Japanese plant or tree grown in miniature form" , "Little Japanese growth" , "Tiny Japanese tree" .)