Sort of sexual transport? (5)
I believe the answer is:
metro
'sort of sexual transport?' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for metro that I've seen before include "Urban railway system" , "French underground" , "Paris underground rail system" , "Parisian underground system" , "what moves many Parisians" .)