Going round and being about to test-drive (9)
I believe the answer is:
besetting
'going round' is the definition.
Although both the answer and definition are present participle verbs, I cannot see how one could define the other.
'being about to test-drive' is the wordplay.
'about' is an insertion indicator.
'to test-drive' becomes 'sett' (I can't explain this - if you can you should believe this answer much more).
'being' placed around 'sett' is 'BESETTING'.
'and' is the link.
Can you help me to learn more?
(Other definitions for besetting that I've seen before include "Troubling; surrounding" , "Causing harassment" , "Persistently troubling" .)