Targeting infantry holding back fire (6)
I believe the answer is:
ignite
'fire' is the definition.
(thesaurus)
'targeting infantry holding back' is the wordplay.
'holding' indicates a hidden word.
'back' says the letters should be written in reverse.
'etingi' is hidden within 'targeting infantry'.
'etingi' back-to-front is 'IGNITE'.
(Other definitions for ignite that I've seen before include "Swan constellation" , "Kindle Fire" , "Cause to start burning" , "Set fire to, light up" , "Combust" .)