Lament having smashed last glass (7)
I believe the answer is:
crystal
'glass' is the definition.
(crystal is a kind of glass)
'lament having smashed last' is the wordplay.
'lament' becomes 'cry'.
'having' means one lot of letters go next to another.
'smashed' is an anagram indicator.
'last' is an anagram of 'stal'.
'cry'+'stal'='CRYSTAL'
(Other definitions for crystal that I've seen before include "Clear material such as quartz" , "Clear mineral, eg, quartz" , "Highly transparent glass" , "Glass-like quartz" , "Quartz, for example" .)