Green’s Dictionary of Slang

balls v.

[balls n. (1) ]

1. to make a mess of.

[UK]M.F. Caulfield Black City 141: I was [...] making sure none of these characters make a balls of things.
[Ire]F. Mac Anna Last of the High Kings 108: The master electrician said that only a maniac could have made such a balls of things.
[Ire]G. Coughlan Everyday Eng. and Sl. [Internet] Balls (n): to mess up, e.g. I made a balls of that job.

2. to secrete near one’s genitals.

[UK]N. Barlay Curvy Lovebox 11: I give her another an’ balls the rest.

In phrases

balls up (v.)

see separate entry.