Marital relations (2-4)
I believe the answer is:
in-laws
'marital relations' is the definition.
(I've seen this in another clue)
'relations' is the wordplay.
I cannot quite see how this works, but
'relations' could be 'laws' (law is a kind of relation) and 'laws' is found in the answer.
The remaining letters 'in' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for in-laws that I've seen before include "Relations by marriage" , "Christmas is when you might bid them welcome" , "Family of your spouse" , "A person's relatives by marriage" , "Relatives by marriage 2-4)" .)