The Saddlers held their own against their high-flying opponents in the first half and had several opportunities to score, including a superb Jake Scrimshaw half-volley that smashed the crossbar.
But the second half performance was well below par as Walsall crumbled under Cheltenham presser and Clarke was disappointed with the ‘soft’ mentality.
He said: “I’m angry. The first half was very good and the second half typified what we’re about.
“Giving a cheap goal away, they score a deflection that leads into the path of their player, the third one is offside.
“For me, in the second half we were miles away from our first half performance.
“I said to my players at half-time, don’t let it be a hard luck story.
“We were in the ascendency and should have a penalty. Hit the crossbar, balls going past their goal quite regularly but not ending up in the back of the net, another story of our season so far.
“Then second half we give them a long throw goal that we’ve worked on all week to defend.
“We looked soft after that and never really got going.”
Controversially, referee Sam Purkiss booked Liam Kinsella in the first half for what he perceived was a dive, when many called for a penalty.
Caolan Lavery suffered the same punishment in the second half and although Clarke admits Lavery’s penalty call was not a spot kick, he was left furious with the Kinsella decision.
“I’ll look at them both but Kins is a stone-waller, without a shadow of a doubt, I’ve seen that one,” Clarke added.
“Lavs looked like he was looking for it to be honest and I’ll have a word with him because I don’t want to see that in my players.
“But the first one is a shocking decision isn’t it.
“We all know Liam Kinsella, he’s been at the club a long time, and for me he’s been brought down.”