Alter, as the Constitution (5)
I believe the answer is:
amend
'alter as the constitution' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for amend that I've seen before include "Make minor improvements to (a document)" , "Make corrections to (eg, document)" , "Change, alter" , "Rectify" , "Change to improve" .)