Hardened to a certain amount of pain and a rude shock! (6)
I believe the answer is:
inured
'hardened to' is the definition.
(I've seen this in another clue)
'pain and a rude shock' is the wordplay.
'pain' becomes 'in' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'shock' is an anagram indicator (a shocked or disturbed version of the letters).
'rude' is an anagram of 'ured'.
'in'+'ured'='INURED'
'a certain amount of' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for inured that I've seen before include "Hardened as by experience" , "Hardened against, toughened" , "Hardened or calloused, being ruined" , "Hardened, perhaps ruined" , "Accustomed to hardship" .)