Banknote left in emptied tray (6)
I believe the answer is:
twenty
'banknote' is the definition.
(eg a twenty pound note)
'left in emptied tray' is the wordplay.
'left' becomes 'went' (left can mean went away).
'in' indicates putting letters inside.
'emptied' means to remove the middle letters.
'tray' with its centre taken out is 'ty'.
'went' going within 'ty' is 'TWENTY'.
(Other definitions for twenty that I've seen before include "previous clue?" , "made by Q on a light blue square" , "No longer a teenager" , "No. between 5 and 1 on dartboard" , "One score" .)