Another's customs (5)
I believe the answer is:
mores
'customs' is the definition.
(I've seen this before)
'another's' is the wordplay.
I cannot really see how this works, but
'another's' could be 'res' (I've seen this in other clues) and 'res' is located in the answer.
The remaining letters 'mo' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for mores that I've seen before include "Conventions, manners" , "Customs, manners" , "O tempora, O - !" , "Customs and conventions of society" , "Social customs of a group" .)