A spectacular last-ball outfield catch from youngster Hannah Darlington helped Sydney Thunder hold on to a nail-biting three-run WBBL win over Melbourne Renegades at Blacktown.

With four required for victory off the final delivery to reel in the Thunder's 8-132, red-hot Renegades captain Jess Duffin (69) skied Rene Farrell miles in the air before 18-year-old Darlington snared a superb tumbling catch on the straight boundary.

The Renegades had slumped to 4-26 and could have been 5-26 had Alex Blackwell hung on to a tough chance at mid-wicket when Duffin was on four.

With the required rate soaring past 10 an over, Duffin, after a justifiably cautious start, led the rearguard fightback, crunching two sixes in her 56-ball gem and finding an able ally in Courtney Webb (32).