Confess some shallow notions (3)
I believe the answer is:
own
'confess' is the definition.
(I've seen this before)
'some shallow notions' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'OWN' is hidden within 'shallow notions'.
(Other definitions for own that I've seen before include "Posses" , "Private" , "Be in legal possession of (3)" , "Possess or confess" , "Possess - recognise - admit" .)