Reference from current employer so I can work elsewhere at the same time

[ohwell02]

Greedy me! My current employer is lovely but very small. They have told me they are pleased with me. I just want to do a few hours elsewhere for an Agency so not letting down current employer as I would always put them first. I would have to get a reference from them before I could work for the Agency.
A friend has suggested working somewhere else completely different
and just saying to current employer that I want to go elsewhere as a type of hobby /experience

[Akire]

The new job will email or write with their company logo and with a specific job title so you can’t really get away with saying it’s a hobby. You can’t give someone a reference without being aware what you are endorsing.

[Struwwelpeter]

Ask your current employer for more hours. When they can't do it ask if they'd mind if you work elsewhere.

If you don't inform them it's almost certainly going to be a disciplinary offence if they find out (check in your employment contract).