Wizard guy conceals all-American private intelligence (8)
I believe the answer is:
magician
'wizard' is the definition.
(synonyms)
'guy conceals all-american private intelligence' is the wordplay.
'guy' becomes 'man ' (guy can informally mean a man).
'conceals' is an insertion indicator.
'all-american private' becomes 'gi' (GI can informally mean a US soldier. I am not sure about the 'all-american' bit.).
'intelligence' becomes 'CIA' (Central Intelligence Agency).
'gi'+'cia'='gicia'
'man' going around 'gicia' is 'MAGICIAN'.
(Other definitions for magician that I've seen before include "Wizard like cartoon Mandrake" , "Conjuror, wizard" , "Conjuror or sorcerer" , "Conjurer, illusionist" , "Conjuror, illusionist" .)