Spooner's sexy apostle is in difficulty (7)
I believe the answer is:
pitfall
'difficulty' is the definition.
(pitfall is a kind of difficulty)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for pitfall that I've seen before include "Unforeseen difficulty" , "Unexpected difficulty or danger" , "Hazard" , "Unexpected problem" , "Hidden danger or difficulty" .)