Sweet tin disappointingly empty (5)
I believe the answer is:
candy
'sweet' is the definition.
(I've seen this before)
'tin disappointingly empty' is the wordplay.
'tin' becomes 'can' ('can' can be a synonym of 'tin').
'empty' says to hollow out the word (remove centre letters).
'disappointingly' with its middle taken out is 'dy'.
'can'+'dy'='CANDY'
(Other definitions for candy that I've seen before include "Sugary sweet" , "Crystallised sugar; US sweets" , "American confectionary" , "Sweet (US)" , "Girl's name (diminutive)" .)