Comfortable about first of these luxuries being expensive (6)
I believe the answer is:
costly
'expensive' is the definition.
(similar in meaning)
'comfortable about first of these luxuries' is the wordplay.
'comfortable' becomes 'cosy' (similar in meaning).
'about' indicates putting letters inside.
'first of' says to take the initial letters.
The initial letters of 'these luxuries' is 'tl'.
'cosy' going around 'tl' is 'COSTLY'.
'being' is the link.
(Other definitions for costly that I've seen before include "Dear" , "Expensive" , "Entailing great loss or sacrifice" , "High-priced" , "Highly priced" .)