Flipping bighead John Campbell? (8)
I believe the answer is:
blooming
'flipping' is the definition.
The answer and definition can be both related to change as well as being present participle verbs.
Maybe you can see an association between them that I can't see?
'bighead john campbell?' is the wordplay.
'bighead' becomes 'b' (head letter of 'big').
'john' becomes 'loo' (both can mean a toilet).
'campbell?' becomes 'ming' (I can't explain this - if you can you should give a lot more credence to this answer).
'b'+'loo'+'ming'='BLOOMING'
Can you help me to learn more?
(Other definitions for blooming that I've seen before include "Euphemistic expletive - in flower" , "Healthy -- flowering" , "Looking healthy" , "Blossoming" .)