Jeer during special date is forbidden (7)
I believe the answer is:
tabooed
'is forbidden' is the definition.
(thesaurus)
'jeer during special date' is the wordplay.
'jeer' becomes 'boo' (I've seen this in another clue).
'during' is an insertion indicator.
'special' is an anagram indicator.
'date' is an anagram of 'taed'.
'boo' going within 'taed' is 'TABOOED'.
(Other definitions for tabooed that I've seen before include "Prevented" , "Banned" .)