What does the cryptic crossword clue "Drop enthralling pretence — some can't tolerate it (7)" mean?

The wordplay uses a deletion. ACT (synonym="ACT") in LOSE (synonym="LOSE") = LACTOSE The answer is LACTOSE.

Drop enthralling pretence — some can't tolerate it (7)

Guardian Cryptic #26527 | 10 Across | 2015-03-24 flower