Collapsed Lung dine on hollow chocolate treat (10)
I believe the answer is:
indulgence
'treat' is the definition.
(thesaurus)
'collapsed lung dine on hollow chocolate' is the wordplay.
'collapsed' indicates anagramming the letters.
'on' says to put letters next to each other.
'hollow' says to hollow out the word (remove centre letters) (the word is hollowed out).
'chocolate' with its middle removed is 'ce'.
'lung'+'dine'='lungdine'
'lungdine' with letters rearranged gives 'indulgen'.
'indulgen'+'ce'='INDULGENCE'
(Other definitions for indulgence that I've seen before include "Gratification, luxury" , "leniency" .)