That’s right. Apparently legendary rock superstar and former Led Zeppelin frontman Robert Plant had been to a Def Leppard show while they were on one of their US legs of their Hysteria World Tour in 1988 and after the gig he asked Steve to join his band.
Ross Halfin, who was one of the main photographers of Def Leppard back in the 80’s was on that tour and was there the night Plant spoke with Steve.

He says: “Steve Clark and I were always very close. He was a true friend of mine.

In Chicago, Robert Plant came to see the show and after watching Steve, Plant asked Steve to join his band. Steve seriously considered this.
Halfin, however suggested Steve should stay with Def Leppard – a much bigger and better band.

[SOURCE: Def Leppard: The Definitive Visual History by Ross Halfin].

Phil Collen has also stated that Robert Plant was interested in and wanted to have Steve join him at one time, during his mini video series “All About Steve Clark” in 2011. When he is asked the question – Did Steve ever consider working or playing with other musicians as a guest musician and Do you think at some point he might have done a solo album/project?, in his answer he mentions the Robert Plant connection: “I know that, em, Robert Plant wanted Steve to play with him at some point”, and he tags on “I think” to the end of that sentence.

Phil Collen has also stated that Robert Plant was interested in and wanted to have Steve join him at one time, during his mini video series “All About Steve Clark” in 2011. When he is asked the question – Did Steve ever consider working or playing with other musicians as a guest musician and Do you think at some point he might have done a solo album/project?, in his answer he mentions the Robert Plant connection: “I know that, em, Robert Plant wanted Steve to play with him at some point”, and he tags on “I think” to the end of that sentence.

[SOURCE: All about Steve Clark Part 2. At 4 min 37 sec.]

For Steve Clark fans, this is actually very big news!! Huge news! Robert Plant wanted Steve Clark!

Rock Stars don’t come much bigger than that. It’s interesting as to why this has never been mentioned before. I would love to have known what Robert Plant had said to Steve and what ideas were in his mind at the time.

I’d also loved to have known what Steve’s own private thoughts about this would’ve been. Such an amazing opportunity for him, to have been able to have had a chance of working with one of his heroes and exploring new musical avenues, To me, this is the type of thing that would’ve been right up Steve’s street.