In opposition! (3)
'in opposition' is the definition.
Both the definition and answer are adverbs. Maybe they are linked in a way I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for out that I've seen before include "Inaccurate - dismissed" , "Away; into public domain" , "Openly gay" , "At fault - dismissed" , "No longer imprisoned" .)
(Other definitions for at loggerheads that I've seen before include "Quarrelling" , "In violent disagreement" , "In violent dispute" , "In confrontation" , "Disagreeing with" .)