What does the cryptic crossword clue "Bug turning up in silo, certainly (1,4)" mean?

The definition is "Bug". The wordplay uses hidden reversed. Hidden reversed in "bug turning up in sILO, CErtainly" The answer is E coli.

Bug turning up in silo, certainly (1,4)

Telegraph Prize Cryptic #3030 | 24 Down | 2019-11-17 flower