do somebody a good turn

do (someone) a good turn

To do something that helps, aids, or benefits another person. If you do someone a good turn, they are much more likely to help you out in the future. John did me a good turn last year, so I'd like to return the favor somehow.
See also: good, turn

do somebody a good ˈturn

be helpful to somebody; do somebody a favour: I did you a good turn, now you do me one.
See also: good, somebody, turn