A note about lake on fire (6)
I believe the answer is:
aflame
'on fire' is the definition.
(synonyms)
'a note about lake' is the wordplay.
'note' becomes 'fame' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'lake' becomes 'L' (geographical abbreviation).
'fame' enclosing 'l' is 'flame'.
'a'+'flame'='AFLAME'
(Other definitions for aflame that I've seen before include "On fire" , "very hot" , "Deeply aroused" , "Ablaze" , "Ardent" .)