Friend or enemy, primarily? Enemy (3)
I believe the answer is:
'enemy' is the definition.
'friend or enemy primarily?' is the wordplay.
'primarily?' indicates taking the first letters (I've seen 'primarily' mean this).
The first letters of 'friend or enemy' is 'FOE'.
(Other definitions for foe that I've seen before include "Antagonist" , "Environmentalists" , "Am archaic enemy" , "friend never!" , "Adversary" .)