Asked to bat, Notts made 133-9 in 44.2 overs, Lee Wilson (3-14) and Chris Fletcher (3-30) sharing six of the wickets.
But rain saw Clipstone given a revised target of 101 in 33 overs and Adam Dutton's 37 not out plus 23 from Fletcher saw them reach 102 from the final over.
With Welbecks' game at Anston rained off, Thoresby took the chance to leapfrog them into second spot by winning by 121 runs at Ordsall Bridon.
Thoresby made 215-7, with 88 for Kieran Walker and 58 for John Skinner, Jake Wells taking 4-40.
But this was another rain-affected afternoon and Bridon were set a revised target of 222 from 42 overs, only to crumble to 100 all out in just 25.3 overs, Will Shaw their only resistance with 38 and Stuart Bullin ending with 4-20 and Azar Hussain 3-8 in just 2.3 overs.
Farnsfield also won with a revised target at Bawtry, where they bowled out the home side for 93.
Asked then to make 86 from 42 overs after rain, Farnsfield did so for five wickets in 31.3 overs, Liam Delaney with 27.
Cuckney seconds won by a commanding 10 wickets against visiting Glapwell.
After Glapwell were bowled out for 168, George Unwin adding 41 and Rob Davison 33, Dan Hadlow with 3-25, Cuckney coasted home as Josh Porter struck a mighty 120 not out and Drew Owen backed him with an unbeaten 43.