Leave in some considerable pain (5)
I believe the answer is:
agony
'considerable pain' is the definition.
'agony' can be an answer for 'pain' (agony is a kind of pain). I am not certain of the 'considerable' bit.
'leave in some' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'in' is an insertion indicator.
'some' becomes 'any' (similar in meaning).
'go' inserted within 'any' is 'AGONY'.
Can you help me to learn more?
(Other definitions for agony that I've seen before include "Severe pain, mental or physical" , "Extreme suffering - kind of aunt" , "Terrible pain" , "Suffering - anguish" , "Really severe pain" .)