Be up against
(Other definitions for oppose that I've seen before include "Act against" , "Resist; disapprove of" , "Resist, contend with" , "Obstruct, resist" , "Resist (someone)" .)
'be up against' is the definition.
(to neighbour something or go beside it)
This is all the clue.
(Other definitions for abut that I've seen before include "Adjoin, border" , "Adjoin at one end" , "Adjoin, press up against" , "Touch, lean on" , "Lean against the odd tuba" .)