Dalziel went 5-0 ahead after 20 minutes through Lewis Marshall’s try, which was unconverted, as the fixture went ahead despite the combined disruptive effects of storms Dudley and Eunice.
A Clydebank penalty then reduced the Motherwell team’s lead to two points but Brad Watson’s penalty for Dalziel put the hosts 8-3 up at half-time.
Calder’s clinching second half score then put the seal on Dalziel’s victory, moving the Motherwell outfit – whose outstanding defence has only conceded 30 points and three tries in their last five games – up to third place in Tennent’s West Division 2 with 36 points from 14 games.
Calder said: “I’m delighted that I’m hopefully still managing to contribute on and off the park.
"The game was very close to being called off. Initially we were meant to be playing on the astroturf 3G pitch, but a late pitch inspection meant the game went ahead on the grass.
"The parks at Dalziel Park are outstanding, so in one respect it didn’t surprise me that the game was on.
“We are very well placed for a strong end to the season. The squad’s getting stronger and stronger.
"We actually had a lot of call-offs on Saturday but it’s a reflection of how strong our squad is becoming that we still played very well.”
To make it a fine double for Dalziel last weekend, their 2nd XV won 49-17 at their Clydebank counterparts.
Meanwhile, rivals Uddingston’s West Division 2 1st XV game at Oban Lorne last Saturday was postponed.
There are no fixtures in the division this weekend.