Make out with Diane regularly seeking penetration (7)
I believe the answer is:
insight
'penetration' is the definition.
(synonyms)
'make out with diane regularly' is the wordplay.
'make out' becomes 'sight' (I've seen this in another clue).
'with' is a charade indicator (letters next to each other).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'diane' are 'in'.
'sight' after 'in' is 'INSIGHT'.
'seeking' is the link.
(Other definitions for insight that I've seen before include "ability to perceive clearly" , "famous Sunday Times team" , "percipience" , "Special knowledge" , "vision" .)