A passage from 'Tristan' (7)
I believe the answer is:
transit
'a passage' is the definition.
(I know that passage can be written as transit)
'from tristan' is the wordplay.
'from' indicates an anagram (from the letters).
'tristan' anagrammed gives 'TRANSIT'.
(Other definitions for transit that I've seen before include "In - - (en route)" , "The carrying of people etc" , "The process of going or conveying" , "Start in for the process of being conveyed" , "Travel" .)