Anger radical joint (6)
I believe the answer is:
rankle
'anger' is the definition.
(I've seen this in another clue)
'radical joint' is the wordplay.
'radical' becomes 'r' (chemistry abbreviation).
'joint' becomes 'ankle' (ankle joint is a kind of joint).
'r'+'ankle'='RANKLE'
(Other definitions for rankle that I've seen before include "Eat into and cause resentment" , "Nag" , "Continue to cause annoyance or bitterness" , "Cause lasting annoyance or resentment" , "get up your nose" .)