In British English – like “licence/license” and “advice/advise” – “practice” is a NOUN and “practise” is a VERB:

NOUN
Safeguarding clients’ personal data should be standard practice in the company.
He has been a lawyer for many years, but he only opened his own practice last month.
“Practice makes perfect.”

VERB
If you want to be a professional pianist you must practise for several hours every day.
So you’re a lawyer? When did you start practising?

In American English, however — and in contrast to the rule for “license” — “practice” is used for both the noun and the verb. “Practise” is a less common spelling variant.