What might emerge from flower could pass quickly (6)
I believe the answer is:
mayfly
'what might emerge from flower' is the definition.
(a mayfly might feed on a flower)
'could pass quickly' is the wordplay.
'could' becomes 'may' (I've seen this before).
'pass quickly' becomes 'fly' (fly can mean to go by quickly).
'may'+'fly'='MAYFLY'
(Other definitions for mayfly that I've seen before include "Ephemeral insect" , "Short-lived spring insect" , "Short-lived insect with delicate wings" .)