What does the cryptic crossword clue "Blissful time, messing about idly on lake (5)" mean?

The wordplay uses an anagram. anagram of IDLY (synonym="IDLY") + L (synonym="L") = IDYLL The answer is IDYLL.

Blissful time, messing about idly on lake (5)

Guardian Cryptic #25599 | 8 Across | 2012-04-02 flower