Subterfuge the concern of wags? (5,8)
I believe the answer is:
funny business
'of wags?' is the definition.
The definition suggests a singular noun which matches the answer.
'subterfuge the concern' is the wordplay.
'subterfuge' becomes 'funny' (I am not sure about this - if you are sure you should believe this answer much more).
'the concern' becomes 'business' (concern can mean a business or company).
'funny'+'business'='FUNNY BUSINESS'
Can you help me to learn more?
(Other definitions for funny business that I've seen before include "Jiggery-pokery" , "Dubious practice - clown's profession?" , "Hanky-panky" , "Shenanigans" , "Deception" .)