It really is a breathtaking experience (8)
I believe the answer is:
asphyxia
'it really is a breathtaking experience' is the definition.
The definition suggests a singular noun which matches the answer.
This is all the clue.
Can you help me to learn more?
(Other definitions for asphyxia that I've seen before include "It's caused by choking or drowning" , "Death by suffocation" , "Suffocation from lack of air in lungs" , "Shortness of breath" , "Suffocation, condition caused by lack of oxygen" .)