Poles in characteristic passage (7)
I believe the answer is:
transit
'passage' is the definition.
(synonyms)
'poles in characteristic' is the wordplay.
'poles' becomes 'ns' (North and South poles).
'in' is an insertion indicator.
'characteristic' becomes 'trait' (I've seen this before).
'ns' inserted within 'trait' is 'TRANSIT'.
(Other definitions for transit that I've seen before include "Travel" , "Pass through; van" , "Passage of a planet across the sun's disc" , "In migration" , "Act of passing across" .)