A great master, but the general is round the bend! (6)
I believe the answer is:
genius
'a great master' is the definition.
'genius' can be an answer for 'master' (genius can mean a master or expert). I'm unsure of the 'a great' bit.
'the general is round the bend' is the wordplay.
'the general' becomes 'gen'.
'round' is an insertion indicator.
'the bend' becomes 'U' (a U-bend is a kind of bend - pipe under sink).
'is' placed around 'u' is 'ius'.
'gen'+'ius'='GENIUS'
'but' acts as a link.
Can you help me to learn more?
(Other definitions for genius that I've seen before include "Brilliant mind" , "Extraordinarily intelligent person" , "great idea?" , "A natural talent" , "Person of extraordinary intellectual power" .)