What does the cryptic crossword clue "Boisterous sons to explain access for improving PC facilities (13)" mean?

The wordplay uses an anagram. anagram of SONS TO EXPLAIN = EXPANSIONSLOT The answer is EXPANSIONSLOT.

Boisterous sons to explain access for improving PC facilities (13)

Independent Cryptic #11725 | 13 Across | 2024-05-09 flower