Damsel is so mesmerising, essentially graceful (7)
I believe the answer is:
lissome
'graceful' is the definition.
(similar in meaning)
'damsel is so mesmerising essentially' is the wordplay.
'essentially' indicates a hidden word (essence can mean the inside of something).
'LISSOME' is hidden in the letters of 'damsel is so mesmerising'.
(Other definitions for lissome that I've seen before include "Willowy" , "Moving supply" , "Oil mess (anag)" , "pliable" , "flexible" .)