A British lounge is brightly lit (6)
I believe the answer is:
ablaze
'brightly lit' is the definition.
(I've seen this in another clue)
'a british lounge' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in BBC).
'lounge' becomes 'laze' (laze can mean to lounge around).
'a'+'b'+'laze'='ABLAZE'
'is' is the link.
(Other definitions for ablaze that I've seen before include "Flaming; on fire" , "On fire - brightly lit" , "Having been fired" , "burnt" , "Burning fiercely" .)