Long rest right, I must be snookered? (3-2)
I believe the answer is:
lie-in
'long rest' is the definition.
'right i must be snookered?' is the wordplay.
'right' becomes 'lien' (legal right).
'must be snookered?' is an insertion indicator.
'lien' enclosing 'i' is 'LIE-IN'.
(Other definitions for lie-in that I've seen before include "Extra zeds in the morning" , "Period in bed longer than usual" , "Extra time in bed" , "Extended overnight rest" , "That extra hour or so in bed?" .)