Changes document in brief recess (7)
I believe the answer is:
reforms
'changes' is the definition.
(reform is a kind of change)
'document in brief recess' is the wordplay.
'document' becomes 'form' (form is a kind of document).
'in' means one lot of letters goes inside another.
'brief' means to remove the last letter.
'recess' becomes 'rest'.
'rest' with its last letter taken away is 'res'.
'form' placed within 'res' is 'REFORMS'.
(Other definitions for reforms that I've seen before include "Makes changes" , "Mends ways, abandons badness" , "Changes for improvement" , "Adjustments" .)