He had high-flying ambition but became unstuck (6)
I believe the answer is:
icarus
'he had high-flying ambition but became unstuck' is the definition.
The definition suggests a singular noun which matches the answer.
'he' is the wordplay.
I cannot really see how this works, but
'he' could be 'car' and 'car' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for icarus that I've seen before include "In Greek myth, he flew too close to the sun and died" , "He was killed flying" , "His false wings melted" , "He died flying" , "One whose wings melted" .)