Smart about means of exerting pressure (6)
I believe the answer is:
clever
'smart' is the definition.
(similar in meaning)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for clever that I've seen before include "Bright; smart" , "easy to teach?" , "Brainy, smart" , "Smar and canny" , "Gifted" .)