Sustain, from exercise, some pain. Cure sought (5)
I believe the answer is:
incur
'sustain' is the definition.
(I've seen this in another clue)
'some pain cure sought' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'INCUR' is hidden in the letters of 'pain cure sought'.
'from exercise' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for incur that I've seen before include "Take on (obligation)" , "Become subject to (something unwelcome)" , "Become responsible for" , "Runic (anag.)" , "Assume" .)