Aid for smoking, herring primarily having gone missing (6)
I believe the answer is:
astray
'missing' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
(Other definitions for astray that I've seen before include "Off the correct path" , "Missing, lost" , "wrong way" , "(Gone) in wrong direction" , "Go . . . . . . - get lost" .)