What does the cryptic crossword clue "Electrons hit with one will be shut in (10)" mean?

The definition is "shut in". The wordplay uses an anagram. anagram of ELECTRONS I = ENCLOISTER; definition: "shut in" The answer is ENCLOISTER.

Electrons hit with one will be shut in (10)

Guardian Cryptic #29006 | 6 Down | 2023-03-01 flower