Black American returns in boat (3)
I believe the answer is:
sub
'boat' is the definition.
(I've seen this before)
'black american returns' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'american' becomes 'us' (abbreviation for United States).
'returns' says the letters should be written backwards.
'b'+'us'='bus'
'bus' reversed gives 'SUB'.
'in' acts as a link.
(Other definitions for sub that I've seen before include "Underwater craft" , "Loan" , "Reserve (abbr)" , "Type of sandwich" , "Underwater boat" .)