Lighter finished as fluid escaped (9)
I believe the answer is:
spillover
'fluid escaped' is the definition.
(fluid that has spilled over)
'lighter finished' is the wordplay.
'lighter' becomes 'spill' (strip of wood for lighting a candle).
'finished' becomes 'over' (over can mean finished or ended).
'spill'+'over'='SPILLOVER'
'as' acts as a link.
(Other definitions for spillover that I've seen before include "unexpected consequence" , "could be too much to cope with" , "excess that's spread around" .)