One taking off is evasive about source of thrust, invoking power (7)
I believe the answer is:
copycat
'one taking off is evasive' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'about source of thrust invoking power' is the wordplay.
I cannot really understand how this works, but
'about' could be 'ca' (abbreviation for circa) and 'ca' is present in the answer.
'of' could be 'o' and 'o' is found within the answer.
'power' could be 'p' (symbol in physics) and 'p' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for copycat that I've seen before include "not the original one" , "Feline imitator" , "Emulator" , "Person imitating another (or cloned pet?)" , "Plagiarist possibly" .)