Crossword Genius

Light sack carried in combat (3,4,2)

Ross

I believe the answer is:

set fire to

'light' is the definition.
(I've seen this before)

'sack carried in combat' is the wordplay.
'sack' becomes 'fire' (both can mean to dismiss from a job).
'carried in' indicates putting letters inside.
'combat' becomes 'set-to' (set-to is a kind of combat).
'fire' put into 'setto' is 'SET FIRE TO'.

(Other definitions for set fire to that I've seen before include "Ignite" , "torch" , "Light" .)

I've seen this clue in The Times.
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