Back from marketing, I start the fire (6)
I believe the answer is:
ignite
'the fire' is the definition.
(I've seen this in another clue)
'back from marketing i start' is the wordplay.
'back' shows that the letters should be reversed in order.
'from' indicates the answer is hidden within the clue.
'etingi' is hidden within 'marketing i start'.
'etingi' backwards is 'IGNITE'.
(Other definitions for ignite that I've seen before include "Torch" , "Combust" , "Swan constellation" , "Cause to start burning" , "Touch off; inflame" .)