Suffer in pain, curiously (5)
I believe the answer is:
incur
'suffer' is the definition.
(to incur is to suffer or experience)
'in pain curiously' is the wordplay.
'in' says the answer is hidden in the clue.
'INCUR' is hidden within 'pain curiously'.
(Other definitions for incur that I've seen before include "Arouse" , "Bring upon oneself - be liable for" , "Become liable to (something) through one's actions" , "Become subject to (something unpleasant)" , "Fall liable to" .)