Hideaway excellent for keeping sides apart (4)
I believe the answer is:
lair
'hideaway' is the definition.
(I've seen this in another clue)
'excellent for keeping sides apart' is the wordplay.
I cannot quite understand how this works, but
'excellent' could be 'ai' (resembles 'A1', old-fashioned term for excellent) and 'ai' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lair that I've seen before include "Rail about wild animal's home" , "enclosure" , "Hiding place, den" , "A nautical hail" , "Earth" .)