Where brothers or sisters may be may be appropriate (2,5)
I believe the answer is:
in order
'be appropriate' is the definition.
('in order' can be similar in meaning to 'appropriate')
'where brothers or sisters may be' is the wordplay.
I cannot quite understand how this works, but
'or' is found in the answer.
This explanation may well be incorrect...
'may' is the link.
Can you help me to learn more?
(Other definitions for in order that I've seen before include "Properly arranged - with the purpose" , "Ready for use; appropriate" , "working properly" , "Brother may be" , "Monks are" .)