Nut's joint presence as principal (8)
I believe the answer is:
headship
'presence as principal' is the definition.
I can't tell whether this definition defines the answer.
'nut's joint' is the wordplay.
'nut's' becomes 'head's' (I've seen this in other clues).
'joint' becomes 'hip' (hip is a kind of joint).
'heads'+'hip'='HEADSHIP'
Can you help me to learn more?
(Other definitions for headship that I've seen before include "Top job in school" , "Rugby position filled by Arnold" , "leading position" , "some teachers aspire to?" , "position of principal" .)