Enemy: soldier perhaps confronting one (4)
I believe the answer is:
anti
'enemy' is the definition.
(I've seen this in another clue)
'soldier perhaps confronting one' is the wordplay.
'soldier perhaps' becomes 'ant' (soldier is a type of ant).
'confronting' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'ant'+'i'='ANTI'
(Other definitions for anti that I've seen before include "One who is against (something)" , "[NO MAN]" , "Prefix meaning against" , "Not favouring" , "Against, informally" .)