Darn discomfort caused by exercise? (6)
I believe the answer is:
stitch
'darn' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for stitch that I've seen before include "Application of needle produces this" , "Sew - sharp pain in side" , "Sudden pain in side after exercise" , "Sharp spasm of pain in the side" , "Tack; pain in side" .)