Tunic, note, simply abandoned (7)
I believe the answer is:
gymslip
'tunic' is the definition.
(gymslip is a kind of tunic)
'note simply abandoned' is the wordplay.
'note' becomes 'g' (musical note).
'abandoned' indicates anagramming the letters.
'simply' with letters rearranged gives 'ymslip'.
'g'+'ymslip'='GYMSLIP'
(Other definitions for gymslip that I've seen before include "Former schoolgirl's wear" , "old girl's uniform" , "Tunic worn by schoolgirls" , "Schoolgirl's PE uniform" , "schoolgirl attire" .)