Left glasses on the throne (3)
I believe the answer is:
loo
'throne' is the definition.
(both can mean a toilet)
'left glasses on' is the wordplay.
'left' becomes 'l' (common abbreviation).
'glasses' becomes 'OO' (OO looks like spectacles).
'on' says to put letters next to each other.
'l'+'oo'='LOO'
'the' acts as a link.
(Other definitions for loo that I've seen before include "In which one goes" , "Privy" , "bog" , "Lavatory - old card game" , "Card-game" .)