White has to be careful how to accept the Pawn. Now 6.d3 is dubious because of 6...h6 7.Nf3 e4 8.Qe2 Nxc4 9.dxc4 Bc5. Black's rapid development will be sufficient compensation for the missing Pawn. Better is 6.Bb5+ c6 7.dxc6 bxc6. Now if 8.Qf3, Black has 8...Rb8 or 8...Qc7. The game usually continues 8.Be2 h6, kicking the Knight away from e4. If 9.Nh3, Black has 9...Bc5, 9...Bd6, or 9...g5.
The main line is 9.Nf3 e4 10.Ne5. In return for the Pawn, Black again has a lead in development and some attacking chances. White has no weaknesses and should pursue the standard strategy for playing against gambits, returning the Pawn at the right moment. For example, after 10...Bd6, a good continuation is 11.f4 and maybe 11...O-O 12.Nc3 Qc7 13.O-O, instead of 11.d4 exd3 12.Nxd3 Qc7.