Press learning of mischief? (7)
I believe the answer is:
implore
'press learning of mischief?' is the definition.
'implore' can be an answer for 'press' (I've seen this before). I'm unsure of the 'learning of mischief?' bit.
'press learning' is the wordplay.
'press' becomes 'imp' (I am not sure about this - if you are sure you should believe this answer much more).
'learning' becomes 'lore' (both can mean tradition or knowledge).
'imp'+'lore'='IMPLORE'
(Other definitions for implore that I've seen before include "Beg earnestly, plead" , "Beg desperately" , "Ask earnestly" , "press" , "Beg earnestly, entreat" .)