It's OK, I'm still at a loss to explain the cause of the sound
Something that should be done to all Unos (that don't have a hydraulic clutch) periodically is this:
- Get some grease, such as the sticky red type, or the slippery grey type, or even the spraycan white type (the spray type won't last as long but is quicker to apply).
- Get your head near the pedals by climbing into the footwell
- Use a fingernail to release the small clip on the clutch pedal pin and slide it off carefully.
- Lift the clutch pedal by hand and remove the cable from it. Let the pedal down to the floor.
- Apply grease generously to the pedal pin, the cable eye, the pedal pivots, and a little to the cable itself where it disappears at the bulkhead
- In the engine bay, apply grease generously to the semicircular block on the clutch arm (on top of the gearbox) and also around the pivot pin for the clutch arm itself (the rust is superficial since it's thick steel). If the cable rubber boot has disintegrated, apply some grease to the inner cable too and inspect for broken strands where the threaded end meets the cable.
- Back inside the car, lift the pedal and refit the cable and clip.
This needs doing once every few years and avoids all sorts of creaks, squawks, and jerkiness with clutch engagement - which, depending on the speed of clutch engagement, may not be noticeable in all gears, so I wonder whether it might be a contributing factor to the odd sound.
If the Uno in question has a hydraulic clutch... you might need to replace the slave cylinder on the gearbox - they rust

See Louie's excellent post at
https://www.fiatforum.com/uno/29364-hydraulic-clutch.html . A real benefit of this forum is that - unlike much of the Internet - this isn't some brief flash-in-the-pan, we're actually here for the long haul

Advice from four years ago is just as useful as advice today...
-Alex