A pair of guys going over Dutch tenor's revision (9)
I believe the answer is:
amendment
'revision' is the definition.
(I've seen this before)
'a pair of guys going over dutch tenor's' is the wordplay.
'pair of' says to double the letters (I've seen 'pair' mean this).
'guys' becomes 'men' (guy can mean a man).
'going over' indicates putting letters inside.
'dutch' becomes 'd' (abbreviation for Dutch).
'tenor's' becomes 't' (this might be a standard abbreviation which I don't know about).
'men' duplicated is 'menmen'.
'menmen' enclosing 'd' is 'mendmen'.
'a'+'mendmen'+'t'='AMENDMENT'
Can you help me to learn more?
(Other definitions for amendment that I've seen before include "Revision" , "the fifth one benefiting Uncle Sam's defendants?" , "Alteration made in a formal document" , "Addition or alteration, to a motion or official document, say" , "a bit of a change!" .)