Basic feature (7)
(Other definitions for element that I've seen before include "For example, gold" , "Fundamental component" , "(One's) preferred or natural environment" , "Basic constituent part" , "Fire (or part of one)" .)
'basic feature' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for essence that I've seen before include "Basic quality" , "Crux" , "Intrinsic nature; four Dn" , "required property" , "Core, most vital part" .)