Slight rattle from rear of car - clutch engaged, moving at low rpm

[ApexSam]

I hear a slight rattle from the rear of the car only audible when windows open when moving (more pronounced driving through confined spaces).

I only hear it when at low rpm (<2.5k), in gear and the clutch is engaged, with the rattle frequency seemingly matching speed, but could be rpm, not certain but the frequency does change.

My car does get wastegate rattle on down rev but this is new, stumped if anyone can advise or point me in the right direction?

Haven't got a video yet but will try to get one shortly.