A Japanese entertainer conceals his age! (6)
I believe the answer is:
geisha
'a japanese entertainer' is the definition.
(geishas traditionally hosted or entertained men)
'conceals his age' is the wordplay.
'conceals' indicates anagramming the letters.
'his'+'age'='hisage'
'hisage' is an anagram of 'GEISHA'.
(Other definitions for geisha that I've seen before include "Japanese hostess trained to entertain men" , "Japanese hostess who entertains men" , "Japanese paid companion" , "Japanese woman trained to be a male companion" , "Japanese girl trained to entertain men" .)