Send Tristan the wrong way round motorway (8)
I believe the answer is:
transmit
'send' is the definition.
('transmit' can be a synonym of 'send')
'tristan the wrong way round motorway' is the wordplay.
'the wrong way' indicates anagramming the letters (I've seen this in other clues).
'round' is an insertion indicator.
'motorway' becomes 'm'.
'tristan' is an anagram of 'transit'.
'transit' enclosing 'm' is 'TRANSMIT'.
(Other definitions for transmit that I've seen before include "Communicate (an idea)" , "put out" , "F. name; Hamlet (anag.)" , "Send from one place to another" , "Pass on (a disease)" .)