Basis to restrict beer and ... (9)
I believe the answer is:
rationale
'basis' is the definition.
(I have seen 'Basis of logic' mean 'rationale' so perhaps 'basis' could also mean 'rationale')
'restrict beer and' is the wordplay.
I cannot really understand how this works, but
'restrict' could be 'ration' (rationing is a kind of restricting) and 'ration' is found within the answer.
'beer' could be 'ale' (type of beer) and 'ale' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for rationale that I've seen before include "Logical reasons (for action)" , "Logical reason for action" , "Basis of logic" , "Reasoned exposition" , "explanation" .)