Withdraw pamphlet in support of Religious Education (7)
I believe the answer is:
retract
'withdraw' is the definition.
(thesaurus)
'pamphlet in support of religious education' is the wordplay.
'pamphlet' becomes 'tract' ('tract' can be a synonym of 'pamphlet').
'in support of' means one lot of letters go next to another (I've seen this in other clues).
'religious education' becomes 're'.
'tract' after 're' is 'RETRACT'.
(Other definitions for retract that I've seen before include "Cancel" , "Sheathe" , "Abjure" , "Take back what was said" , "Eat one's words" .)