Reports are obtained in slang (5)
I believe the answer is:
argot
'slang' is the definition.
(synonyms)
'reports are obtained in' is the wordplay.
'reports' becomes 'r' (this might be a standard abbreviation which I don't know about).
'are' becomes 'a' (short for 'are', historical unit of measurement).
'obtained' becomes 'got' ('get' can be a synonym of 'obtain').
'in' means one lot of letters goes inside another.
'a'+'got'='agot'
'r' put inside 'agot' is 'ARGOT'.
Can you help me to learn more?
(Other definitions for argot that I've seen before include "Particular group's jargon" , "Slang of a particular group, originally thieves" , "Talk of thieves" , "Father or mother" , "Kind of slang" .)