At home, instruct, excite oddly, showing brainpower (9)
I believe the answer is:
intellect
'brainpower' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'at home instruct excite oddly' is the wordplay.
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'instruct' becomes 'tell' (I've seen this before).
'oddly' means one should take alternating letters.
The alternating letters of 'excite' are 'ect'.
'in'+'tell'+'ect'='INTELLECT'
'showing' is the link.
Can you help me to learn more?
(Other definitions for intellect that I've seen before include "Faculty of reasoning" , "Cognitive faculty" , "Power of the mind" , "Mental power" , "Person with brilliant mind" .)