Showing opposition -- it's rising in difficult situation (7)
I believe the answer is:
hostile
'showing opposition' is the definition.
(I've seen this before)
'it's rising in difficult situation' is the wordplay.
'rising' is a reversal indicator (going up in a down clue).
'in' indicates putting letters inside.
'difficult situation' becomes 'hole'.
'its' back-to-front is 'sti'.
'sti' inserted inside 'hole' is 'HOSTILE'.
(Other definitions for hostile that I've seen before include "Aggressive" , "harsh" , "Enemy" , "Belligerent" , "Unkind" .)