Beg mischief-maker to take on new role (7)
I believe the answer is:
implore
'beg' is the definition.
(synonyms)
'mischief-maker to take on new role' is the wordplay.
'mischief maker' becomes 'imp' (I've seen this in another clue).
'to take on' means one lot of letters go next to another.
'new' indicates anagramming the letters.
'role' is an anagram of 'lore'.
'imp'+'lore'='IMPLORE'
(Other definitions for implore that I've seen before include "Beg earnestly, beseech" , "More lip (anag)" , "Beg desperately" , "Ask earnestly" , "Beg earnestly, plead" .)