In folklore a delectable mountain nymph (5)
I believe the answer is:
oread
'mountain nymph' is the definition.
(I've seen this before)
'in folklore a delectable' is the wordplay.
'in' says the answer is hidden in the clue.
'OREAD' is hidden in the letters of 'folklore a delectable'.
(Other definitions for oread that I've seen before include "mountainous girl" , "spirit at peak?" , "classically beautiful girl" , "Maid of the Mountains" , "O dear, a strange mountain nymph" .)