Exercise in the gym? Don't look so sad (4-2)
I believe the answer is:
chin-up
'exercise' is the definition.
(I know that chin-up is a bodyweight exercise)
'in the gym? don't look so sad' is the wordplay.
I cannot quite see how this works, but
'in' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for chin-up that I've seen before include "Remain cheerful - mandible aloft" , "Exhortation to stay cheerful in difficult circumstances" , "Don't despair" , "Show courage with elevated mandible" , "Be of good cheer - elevate mandible" .)