Output of sewer a running sore? (6)
I believe the answer is:
stitch
I believe this is a double definition.
'output of sewer' is the first definition.
(as in sewing)
'a running sore?' is the second definition.
(pain caused by exercise)
(Other definitions for stitch that I've seen before include "Use a needle - pain in the side" , "Interlinking loop of yarn" , "A sewer may produce such" , "Link, loop or knot made in knitting or sewing" , "herringbone?" .)