To an extent, turns poor tommies back into fighting force (6)
I believe the answer is:
troops
'fighting force' is the definition.
(thesaurus)
'to an extent turns poor tommies back' is the wordplay.
'to an extent' indicates a hidden word.
'back' says the letters should be written backwards.
'spoort' can be found hidden inside 'turns poor tommies'.
'spoort' written backwards gives 'TROOPS'.
'into' acts as a link.
(Other definitions for troops that I've seen before include "men" , "Soldiers, armed forces" , "Cavalry" , "Groups of soldiers" , "Military divisions" .)