Trained person if also rubbish (12)
I believe the answer is:
professional
'trained' is the definition.
(trained for a profession)
'person if also rubbish' is the wordplay.
'rubbish' indicates anagramming the letters (a poor quality or rubbish spelling of the letters).
'person'+'if'+'also'='personifalso'
'personifalso' is an anagram of 'PROFESSIONAL'.
(Other definitions for professional that I've seen before include "Expert - one paid in sport etc" , "Paid sportsman" , "someone performing for a fee maybe" , "Not amateur" , "Skilful, competent" .)