Clue: Dark, 'orrible place to the north hiding bright light — quite the opposite (6)
Answer: SULLEN
Explanation: Definition: Dark
An envelope ('hiding') of LLE, a reversal ('to the north' in a down light) of 'ELL (' 'orrible place') in SUN ('bright light'), with 'quite the opposite' to account for the particles being presented in the reverse order.