Spider wrote in :

You would have to wait for cooler, moister weather, but one way would be
to cut a turf of your clover lawn and swap it with a turf of your
un-clovered lawn. Once established, the clover would soon colonise the
plain grassy areas. Another way would be to mow without the grass
collection box (again, when the ground is reliably moist). You should
find that the clover fragments root into the turf and establish. This
is what happens with my lawn when I leave the grass box off.

That's interesting. I will have to try that, rather than fork out good
money for seed.

Al