One who might organise sex with topless duke (8)
I believe the answer is:
unionist
'one who might organise' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'sex with topless duke' is the wordplay.
'sex' becomes 'union' (union is a kind of sex).
'with' means one lot of letters go next to another.
'topless' means to remove the first letter.
'duke' becomes 'fist' (put up your dukes).
'fist' with its first letter taken away is 'ist'.
'union'+'ist'='UNIONIST'
Can you help me to learn more?
(Other definitions for unionist that I've seen before include "Person supporting the political links between Great Britain and Northern Ireland" , "not Republican" , "Supporter of the cohesion of England, Wales, Scotland and Northern Ireland" , "Civil warmonger" , "Politician" .)