Unable to perceive pen after drinking bout (9)
I believe the answer is:
blindfold
'unable to perceive' is the definition.
I can't tell whether this definition defines the answer.
'pen after drinking bout' is the wordplay.
'pen' becomes 'fold' (fold is a kind of pen).
'after' is a charade indicator (letters next to each other).
'drinking bout' becomes 'blind' (I can't justify this - if you can you should believe this answer much more).
'fold' after 'blind' is 'BLINDFOLD'.
Can you help me to learn more?
(Other definitions for blindfold that I've seen before include "Stop seeing" , "headband" , "Piece of cloth etc to prevent one seeing" , "bandage" , "Stop one looking" .)