What does the cryptic crossword clue "Dressed in cap, Peter is trainee (10)" mean?

The definition is "trainee". The wordplay uses an anagram. anagram of IN + CAP, + PETER = APPRENTICE; definition: "trainee" The answer is APPRENTICE.

Dressed in cap, Peter is trainee (10)

Daily Mail Cryptic #17247 | 2 Down | 2023-12-11 flower