I'm not sure poking champion knight shows brains (6)
I believe the answer is:
acumen
'i'm not sure poking champion knight shows brains' is the definition.
I can't tell whether this defines the answer.
'i'm not sure poking champion knight' is the wordplay.
'i'm not sure' becomes 'um' (expression of hesitation).
'poking' is an insertion indicator (poke can mean to create a hole in).
'champion' becomes 'ace' (both can mean a person excelling at something).
'knight' becomes 'n' (chess abbreviation).
'um' put into 'ace' is 'acume'.
'acume'+'n'='ACUMEN'
Can you help me to learn more?
(Other definitions for acumen that I've seen before include "Intellectual sharpness as in business" , "The ability to make good and quick decisions" , "Mental sharpness as in business" , "Keen intelligence" , "'Keenness, depth of perception (6)'" .)