I'll be heard in the passage (5)
I believe the answer is:
aisle
'passage' is the definition.
(aisle is a kind of passage)
'i'll be heard' is the wordplay.
'be heard' indicates a 'sounds like' (homophone) clue.
'ill' sounds like 'AISLE'.
'in the' acts as a link.
(Other definitions for aisle that I've seen before include "Supermarket feature" , "'Passage, gangway (5)'" , "Way between seating areas" , "that would-be bride hopes to make it up!" , "Passage between seating areas" .)