Front line deviously reshaped round middle of war (9)
I believe the answer is:
spearhead
'front line' is the definition.
(thesaurus)
'deviously reshaped round middle of war' is the wordplay.
'deviously' indicates anagramming the letters (I've seen this in other clues).
'round' indicates putting letters inside.
'middle of' says to take the centre.
The centre of 'war' is 'a'.
'reshaped' anagrammed gives 'spearhed'.
'spearhed' going around 'a' is 'SPEARHEAD'.
(Other definitions for spearhead that I've seen before include "Advanced troops" , "come first" , "Group leading an attack" , "front" , "tip on manual weapon" .)