Puzzle's meaning not essentially obscure (6)
I believe the answer is:
enigma
'puzzle's' is the definition.
(I've seen this before)
'meaning not essentially obscure' is the wordplay.
'not essentially' means to remove the middle letters (without the essence/centre letters).
'obscure' indicates an anagram.
'meaning' with its centre taken out is 'meaing'.
'meaing' anagrammed gives 'ENIGMA'.
(Other definitions for enigma that I've seen before include "Mysterious person/thing" , "Something mysterious and puzzling" , "closed book" , "Puzzle of gamine (6)," , "Mysteriously puzzling person or thing" .)