Sailor's lounge on fire (6)
I believe the answer is:
ablaze
'on fire' is the definition.
('ablaze' can be a synonym of 'on fire')
'sailor's lounge' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'lounge' becomes 'laze' (I've seen this before).
'ab'+'laze'='ABLAZE'
(Other definitions for ablaze that I've seen before include "filled with anger" , "Burning fiercely" , "Fiery" , "Well-lit" , "being toasted?" .)