I leave one sat expectantly in front of Parsifal with opera glasses (3)
I believe the answer is:
poo
'i leave one sat expectantly' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'front of parsifal with opera glasses' is the wordplay.
'front of' suggests taking the first letters (the letter at the front of the word).
'with' is a charade indicator (letters next to each other).
'opera glasses' becomes 'oo' (I am not sure about this - if you are sure you should believe this answer much more).
The first letter of 'parsifal' is 'p'.
'p'+'oo'='POO'
'in' is the link.
Can you help me to learn more?
(Other definitions for poo that I've seen before include "Expression of disgust (at, eg, bad smell)" , "Expression of disgust; sounds like bear" , "number two?" .)