Mad about obstacle (3)
I believe the answer is:
dam
'obstacle' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'mad about' is the wordplay.
'about' says the letters should be written backwards.
'mad' written backwards gives 'DAM'.
Can you help me to learn more?
(Other definitions for dam that I've seen before include "Barrier to contain the flow of water" , "Mother of quadruped" , "Mother - barrier" , "Water barrier, quite mad" , "River blockage" .)