Job function reportedly introduces guidance (8)
I believe the answer is:
signpost
'guidance' is the definition.
(a signpost offers guidance)
'job function reportedly introduces' is the wordplay.
'job' becomes 'post' (post is a kind of job).
'function' becomes 'sine' (mathematical function).
'reportedly' shows a homophone (sound like).
'introduces' means one lot of letters go next to another (some letters come before or introduce others).
'sine' sounds like 'sign'.
'post' after 'sign' is 'SIGNPOST'.
(Other definitions for signpost that I've seen before include "Direction pointer" , "It shows the way" , "Indication of direction" , "Clue" , "indication how to progress" .)