Having litres to drink, help brought in as specified (4,4)
I believe the answer is:
laid down
'specified' is the definition.
(I've seen this before)
'having litres to drink help brought in' is the wordplay.
I cannot really see how this works, but
'litres' could be 'l' (abbreviation) and 'l' is found in the answer.
'drink' could be 'down' (to down something can mean to drink it quickly) and 'down' is found in the answer.
'help' could be 'aid' (synonyms) and 'aid' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'as' is the link.
Can you help me to learn more?
(Other definitions for laid down that I've seen before include "Ordained" , "Stipulated - deposited" , "Insisted upon - abandoned" , "specified" .)