Sanction wordplay and strange hints about Matilda (10)
I believe the answer is:
punishment
'sanction' is the definition.
(I've seen this before)
'wordplay and strange hints about matilda' is the wordplay.
'wordplay' becomes 'pun' (synonyms).
'and' says to put letters next to each other.
'strange' indicates an anagram.
'about' indicates putting letters inside.
'matilda' becomes 'me' (where the crossword setter is 'Matilda').
'hints' with letters rearranged gives 'ishnt'.
'ishnt' placed around 'me' is 'ishment'.
'pun'+'ishment'='PUNISHMENT'
(Other definitions for punishment that I've seen before include "See 6" , "That may be fine" , "Penalty" , "Beating" , "Discipline" .)