Took down a note, not being negative (3)
I believe the answer is:
ate
'took down' is the definition.
(I've seen this in another clue)
'a note not being negative' is the wordplay.
'not' is a deletion indicator.
'being negative' becomes 'no'.
'note' with 'no' removed is 'te'.
'a'+'te'='ATE'
(Other definitions for ate that I've seen before include "Greek goddess of mischief" , "Tea (anag.)" , "Ingested" , "Munched" , "Had at meal" .)