Play without stress (8)
I believe the answer is:
underact
'play' is the definition.
(underacting is a kind of playing)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for underact that I've seen before include "Deliver role in a restrained manner" , "put little into role" , "Of thespian, perform with excessive restraint" , "Minimise part played" , "Play down for effect" .)