Relating to large masses may be called wisdom (5)
I believe the answer is:
Here is my best explanation:
This clue is a double definition.
'relating to large masses' is the first definition.
(molar can mean relating to mass)
'may be called wisdom' is the second definition.
(as in wisdom teeth)
(Other definitions for molar that I've seen before include "A grinding tooth", "Grinding tooth in the back of a mammal's mouth", "Dealing with masses", "Moral (anag.)", "that could be capped", "Type of tooth", "Back tooth", "part of the daily grind", "Chewer and grinder" and "Large tooth".)