Birdy Suet Ball holder, like the one from the Birdfy Pro accessories kit.

Put your suet in there and woodpeckers will come eat it.

Print with supports and be careful to clean them off completely so the twist lock works.

Recommended: PETG w/ Supports at .20 or .15mm.

Update:
Minor update to clean things up a bit and make it more printable.
Also, check out the new version here Birdfy Suet Ball v2
If you are having trouble with supports and the twist lock.