Ordinal left with less information originally, after amendment (7)
I believe the answer is:
twelfth
'ordinal' is the definition.
('twelfth' can be similar in meaning to 'ordinal')
'left with less information originally after amendment' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'left' is 'elft' which is present in the answer.
'with' could be 'w' (abbreviation) and 'w' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for twelfth that I've seen before include "day of parades" , "for the night? Sort of" , "Sewn join" , ""Drummers drumming" day of Christmas" , "- Night (Shakespeare)" .)