Obligation to include separate bits of toilet, not as a one-off? (5)
I believe the answer is:
'obligation to include separate' is the definition.
I can't tell whether this defines the answer.
'bits of toilet not as a one-off?' is the wordplay.
'bits of' suggests taking the first letters.
'not as' becomes 'w' (I can't justify this - if you can you should give a lot more credence to this answer).
'a one off?' becomes 'ice' (I've seen this in another clue).
The initial letter of 'toilet' is 't'.
Can you help me to learn more?
(Other definitions for twice that I've seen before include "Doubly" , "Two times" , "You only live -- (film)" , "Double in quantity" .)