Contribution towards ultra-cheap passage (7)
I believe the answer is:
trachea
'passage' is the definition.
(I've seen this before)
'contribution towards ultra-cheap' is the wordplay.
'contribution towards' indicates the answer is hidden within the clue (the solution contributes letters to the clue).
'TRACHEA' is hidden within 'ultra cheap'.
(Other definitions for trachea that I've seen before include "get air supply through this" , "air passage" , "body part" , "Tube carrying air to the lungs" , "where air passes" .)