Walls of chapel best trimmed with romantic illumination (9)
I believe the answer is:
candlelit
'walls of chapel' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'best trimmed with romantic illumination' is the wordplay.
'best' becomes 'elite' (elite can mean the very best of a group).
'trimmed' says to take the centre (the edge letters are trimmed off).
'with' says to put letters next to each other.
'romantic illumination' becomes 'candle' (I am not sure about this - if you are sure you should believe this answer much more).
The centre of 'elite' is 'lit'.
'lit' after 'candle' is 'CANDLELIT'.
Can you help me to learn more?
(Other definitions for candlelit that I've seen before include "Softer ambient setting" , "With dim illumination" , "dim but romantic?" , "romantic setting" , "Dimly illuminated" .)