More inquisitive about one not so quiet (7)
I believe the answer is:
noisier
'not so quiet' is the definition.
('noisy' can be the opposite of 'quiet' so perhaps 'noisier' is reasonable for 'not so quiet')
'more inquisitive about one' is the wordplay.
'more inquisitive' becomes 'nosier' (nosy means overly inquisitive or curious).
'about' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'nosier' going around 'i' is 'NOISIER'.
(Other definitions for noisier that I've seen before include "more deafening!" , "More of a racket" , "Louder" , "More loud" , "Perhaps more disturbing" .)