So in love as to be transformed in demeanour (9)
I believe the answer is:
enamoured
'so in love' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs can occasionally define each other.
'to be transformed in demeanour' is the wordplay.
'demeanour' can be anagrammed to 'ENAMOURED'.
But, I am not sure how the anagram is indicated.
'as' is the link.
Can you help me to learn more?
(Other definitions for enamoured that I've seen before include "Filled with love" , "Smitten" , "Bewitched" , "Our mean Ed (anag.)" , "Charmed" .)