Joint in middle of Warsaw causes annoyance (7)
I believe the answer is:
rankles
'causes annoyance' is the definition.
Although both the answer and definition are verbs in their -s form, I can't understand how they can define each other.
'joint in middle of warsaw' is the wordplay.
'joint' becomes 'ankle' (joint of the body).
'in' is an insertion indicator.
'middle of' means to look at the middle letters.
The middle of 'warsaw' is 'rs'.
'ankle' put inside 'rs' is 'RANKLES'.
Can you help me to learn more?
(Other definitions for rankles that I've seen before include "Riles" , "Goes on vexing" , "Continues to hurt" , "Causes lasting and bitter annoyance" .)