Soldier, perhaps, I will be against (4)
I believe the answer is:
anti
'against' is the definition.
(prefix meaning against)
'soldier perhaps i' is the wordplay.
'soldier perhaps' becomes 'ant' (soldier is a type of ant).
'ant'+'i'='ANTI'
'will be' is the link.
(Other definitions for anti that I've seen before include "Definitely not pro" , "Against, informally" , "Not in favor of" , "one opposing?" , "'No' voter" .)