Council at which it's not entirely easy to drop off to sleep! (5)
I believe the answer is:
synod
'council at which it's not entirely easy' is the definition.
'synod' can be an answer for 'council' (synod is a kind of council). I am not certain of the remainder of the definition.
'drop off to sleep' is the wordplay.
'drop off' becomes 'sy' (I can't justify this - if you can you should believe this answer much more).
'to sleep' becomes 'nod' (I've seen this before).
'sy'+'nod'='SYNOD'
'to' is the link.
Can you help me to learn more?
(Other definitions for synod that I've seen before include "Church assembly" , "Forum for discussing" , "Church council" , "cloth gathered here" , "Ecclesiastical gathering" .)