Function organiser expecting attendees to be late (10)
I believe the answer is:
undertaker
'function' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'organiser expecting attendees to be late' is the wordplay.
I cannot really understand how this works, but
'be' could be 'take' (taking is a kind of being) and 'take' is found within the answer.
'late' could be 'd' and 'd' is present in the answer.
This explanation may well be incorrect...
(Other definitions for undertaker that I've seen before include "He'll deal with passing" , "One passing dangerously" , "Funeral director" , "One making promises" .)