What is this part?

[vintovka]

Hello everyone,

I have recently had a leak under the sink and a short investigation I found this part on the photo cracked. This is a part of the cold water flow and goes straight to the tap.
For self-training purposes (I have currently zero experience in plumbing) I thought that maybe I could replace it myself, but I don't know what is this part.
Can someone please help me identify it?
Also, does it look like someone unexperienced like me can fix this? Any related links, guides, videos, etc are welcome.

Thanks!

 

[exedon2]

Looks like a bit of a bodge to be honest
Pic from a bit further back would be useful to identify pipework coming from right of pic.

 

[vintovka]

Sure, there is a larger context.

 

[exedon2]

Needs carefully measuring but looking at scale that's probably 8mm copper to 15mm copper. You need a 8mm x 15mm compression connector ,search screwfix . Probably need a short end of 15mm copper tube and compression olive to renew back to tee.
Could also be 10mm copper so measure carefully!

 

[ShaunCorbs]

Just needs the male iron remaking with more ptfe tape (the middle joint on the reducer)

 

[exedon2]

First pic seems to show a split on the female connector?

 

[vintovka]

It looks like there are two reducers: 15mm to 1/2 inch and 1/2 inch to 6mm, the latter needs to be replaced. It's kind of difficult to find that reducer or 15 mm to 6mm straightaway, so I wil have to search for other combinations too.