Pains I described holding stomach (7)
I believe the answer is:
insides
'stomach' is the definition.
(I've seen this before)
'pains i described holding' is the wordplay.
'holding' indicates the answer is hidden within the clue.
'INSIDES' is hidden within 'pains i described'.
(Other definitions for insides that I've seen before include "Entrails" , "guts" , "stomach" .)