Fall asleep beside passage, leading to aviation emergency (5-7)
I believe the answer is:
crash-landing
'aviation emergency' is the definition.
(eg a plane landing)
'fall asleep beside passage' is the wordplay.
'fall asleep' becomes 'crash' (I've seen this in another clue).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'passage' becomes 'landing' (I have seen 'Upstairs passage ' mean 'landing' so perhaps 'passage' could also mean 'landing').
'crash'+'landing'='CRASH-LANDING'
'leading to' is the link.
(Other definitions for crash-landing that I've seen before include "Emergency descent" , "Emergency setting down of aircraft with resultant damage" , "(Plane's) emergency return to earth" .)