Fool soldier switched race date (11)
I believe the answer is:
assignation
'date' is the definition.
(I have seen 'The date' mean 'assignation' so perhaps 'date' could also mean 'assignation')
'fool soldier switched race' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'soldier' becomes 'GI' (term for US soldier).
'switched' says the letters should be written in reverse.
'race' becomes 'nation' (both can mean a national or ethnic group).
'gi' in reverse letter order is 'ig'.
'ass'+'ig'+'nation'='ASSIGNATION'
(Other definitions for assignation that I've seen before include "Secret rendezvous" , "Go in as saint (anag.)" , "The date" , "Secret meeting" , "clandestine meeting" .)