Stone had the final attempt in the design of flight engines (8)
I believe the answer is:
rocketry
'design of flight engines' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'stone had the final attempt' is the wordplay.
'stone' becomes 'rock' (synonyms).
'had' is a charade indicator (letters next to each other).
'final' suggests the final letters.
'attempt' becomes 'try' (synonyms).
The final letter of 'the' is 'e'.
'rock'+'e'+'try'='ROCKETRY'
'in the' acts as a link.
Can you help me to learn more?
(Other definitions for rocketry that I've seen before include "Complex science" , "Study of space vehicles" , "Clever science" , "Branch specialised in launching" , "Science concerned with missiles" .)