Poles covered by characteristic passage (7)
I believe the answer is:
transit
'passage' is the definition.
('transit' can be a synonym of 'passage')
'poles covered by characteristic' is the wordplay.
'poles' becomes 'ns' (North and South poles).
'covered by' means one lot of letters goes inside another.
'characteristic' becomes 'trait' (I've seen this before).
'ns' placed within 'trait' is 'TRANSIT'.
(Other definitions for transit that I've seen before include "The process of going or passing - sic . . . . . . . gloria mundi" , "Passage of a planet across the sun's disc" , "Passage of heavenly body" , "The act of carrying from one place to another" , "Pass through; van" .)