Flower cult essentially adopted by crown (5)
I believe the answer is:
tulip
'flower' is the definition.
(tulip is a type of flower)
'cult essentially adopted by crown' is the wordplay.
'essentially' means to look at the middle letters.
'adopted by' indicates putting letters inside (I've seen this in other clues).
'crown' becomes 'tip' (synonyms).
The central letters of 'cult' are 'ul'.
'ul' put into 'tip' is 'TULIP'.
(Other definitions for tulip that I've seen before include "Dutch export" , "Plant of the lily family with a single showy flower" , "Garden flower from bulb" , "Flowering bulb (from Amsterdam?)" , "Spring-blooming plant" .)