Jack and Roy going round in a whirl? (6)
I believe the answer is:
rotary
'jack' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'roy going round in a whirl?' is the wordplay.
'going round' is an insertion indicator (some letters go around others).
'in a whirl?' becomes 'tar' (I can't justify this - if you can you should give a lot more credence to this answer).
'roy' going around 'tar' is 'ROTARY'.
'and' is the link.
Can you help me to learn more?
(Other definitions for rotary that I've seen before include "Gyratory" , "Revolving round an axis" , "International club" , "Moving in a circle" , "Spinning" .)