Nothing doing! (Tricky Dick) (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
nixon
'tricky dick' is the definition.
The definition suggests a singular noun which matches the answer.
'nothing doing' is the wordplay.
'nothing' becomes 'nix' (nix can mean nothing).
'doing' becomes 'on' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nix'+'on'='NIXON'
Can you help me to learn more?
(Other definitions for nixon that I've seen before include "Disgraced US president" , "Ex-US president" , "See 16 Down" , "US president - subject of an opera by John Adams" , "Watergate US president" .)