Take back pamphlet produced by Royal Engineers (7)
I believe the answer is:
retract
'take back' is the definition.
(as in retracting a statement)
'pamphlet produced by royal engineers' is the wordplay.
'pamphlet' becomes 'tract' (synonyms).
'produced by' says to put letters next to each other.
'royal engineers' becomes 'RE' (abbreviation).
'tract' after 're' is 'RETRACT'.
(Other definitions for retract that I've seen before include "Sheathe" , "Eat one's words" , "Pull back (statements or claws, perhaps)" , "Take back (statement)" , "Withdraw, take back" .)