Cycling groups go in for wife-swapping (5)
I believe the answer is:
swing
'for wife-swapping' is the definition.
I can't tell whether this definition defines the answer.
'cycling groups go in' is the wordplay.
'cycling groups' becomes 'w' (I can't explain this - if you can you should believe this answer much more).
'go' becomes 'sing' (singing is a kind of going).
'in' indicates putting letters inside.
'w' put within 'sing' is 'SWING'.
Can you help me to learn more?
(Other definitions for swing that I've seen before include "Shift opinions; hang" , "Big band jazz" , "Golfer may want to perfect this" , "Move like a pendulum" , "something in the playground" .)