Set off from desirable avenue (5)
I believe the answer is:
leave
'set off' is the definition.
(I've seen this in another clue)
'from desirable avenue' is the wordplay.
'from' indicates a hidden word.
'LEAVE' can be found hidden inside 'desirable avenue'.
(Other definitions for leave that I've seen before include "Clearance" , "Don't take - time off" , "Renounce" , "taken by those on the way out" , "Depart - on office holidays?" .)