Expert brought up in Monte Carlo (3)
I believe the answer is:
ace
'expert' is the definition.
(ace can informally mean very good)
'brought up in monte carlo' is the wordplay.
'brought up' says the letters should be written in reverse (in a down clue, letters go up).
'in' indicates a hidden word.
'eca' is hidden in the letters of 'monte carlo'.
'eca' reversed gives 'ACE'.
(Other definitions for ace that I've seen before include "fighter pilot" , "strained" , "unit > of highest quality" , "Tennis serve that the opponent can't reach" , "Winning serve; hole in one" .)