Like S&M, perhaps, in old courts? (7)
I believe the answer is:
assizes
'old courts?' is the definition.
(I've seen this before)
'like sm perhaps' is the wordplay.
'like' becomes 'as'.
'sm perhaps' becomes 'sizes' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'as'+'sizes'='ASSIZES'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for assizes that I've seen before include "Former court sessions" , "Precursor of Crown Courts" , "Judicial sessions (hist.)" , "Old county court sessions chaired by itinerant judges" , "Local courts" .)