Formality by the gang, it's cold treatment (3,4)
I believe the answer is:
ice pack
'cold treatment' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'formality by the gang' is the wordplay.
'formality' becomes 'ice' (I've seen this before).
'by' says to put letters next to each other.
'the gang' becomes 'pack' ('pack' can be a synonym of 'gang').
'ice'+'pack'='ICE-PACK'
'it's' is the link.
Can you help me to learn more?
(Other definitions for ice pack that I've seen before include "This could reduce swelling" , "may be of use for a flush" , "Cooling application" , "number of arctic wolves?" , "Frozen mass" .)