I’m quiet — is he primarily mischievous? (6)
I believe the answer is:
impish
'mischievous?' is the definition.
(I know that mischievous can be written as impish)
'i'm quiet is he primarily' is the wordplay.
'i'm' becomes 'i' (I've seen this in other clues).
'quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'is he' becomes 'imp' (I am not sure about this - if you are sure you should believe this answer much more).
'primarily' is a charade indicator (letters next to each other).
'i'+'sh'='ish'
'ish' put after 'imp' is 'IMPISH'.
Can you help me to learn more?
(Other definitions for impish that I've seen before include "Mischievous like small fairy" , "Naughty" , "Wicked" , "saucy" , "troublesome" .)