A set preliminary (7)
I believe the answer is:
shampoo
This clue might be a double definition.
'a set' is the first definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'preliminary' is the second definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
Can you help me to learn more?
(Other definitions for shampoo that I've seen before include "Hair lotion" , "Bathroom preparation" , "Carpet/hair cleanser" , "Hair or carpet cleaner" , "Hair-cleansing agent" .)