(T)horny problem? (7)
I believe the answer is:
dilemma
'thorny problem?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dilemma that I've seen before include "tricky position" , "Difficulty (with two choices?)" , "Problem (with horns?)" , "23 [SPOT]" , "Situation requiring a choice between (equally unpleasant) options" .)