Nobody in particular (7)
'nobody in particular' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for someone that I've seen before include "An unknown person" , "Important person" , "big cheese" , "Celebrity" , "Unspecified person" .)
(Other definitions for anyone that I've seen before include "Whosoever" , "Pick a person - doesn't matter who" , "Whoever" , "Has ...here seen Kelly (music hall song)" , "A person in general" .)