Bonus for American after record turnover (4)
I believe the answer is:
plus
'bonus' is the definition.
(I know that bonus can be written as plus)
'american after record turnover' is the wordplay.
'american' becomes 'US' (abbreviation for United States).
'after' means one lot of letters go next to another.
'record' becomes 'L-P' (abbreviation for long play record).
'turnover' shows that the letters should be reversed in order (the letters turn over).
'lp' reversed gives 'pl'.
'us' after 'pl' is 'PLUS'.
'for' is the link.
(Other definitions for plus that I've seen before include "sign of more to come" , "An advantage; positive" , "Positive thing" , "advantageous" , "Benefit" .)