Ah! Geometry transformational in maths branch! (4,6)
I believe the answer is:
game theory
'maths branch' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'ah geometry transformational' is the wordplay.
'ah geometry' can be anagrammed to 'GAME THEORY'.
However, I am not clear how this is indicated.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for game theory that I've seen before include "this might help with decision making" , "part of mathematics" .)