Former tie broken in WW1 battlefield (8)
I believe the answer is:
sometime
'former' is the definition.
(I know that former can be written as sometime)
'tie broken in ww1 battlefield' is the wordplay.
'broken' indicates an anagram.
'in' indicates putting letters inside.
'ww1 battlefield' becomes 'somme' (I've seen this before).
'tie' is an anagram of 'eti'.
'eti' put inside 'somme' is 'SOMETIME'.
(Other definitions for sometime that I've seen before include "On a future unnamed occasion" , "On an undetermined date in the future" , "At a future unknown period" , "An indeterminate date in the future" , "In the future, we don't know when" .)