Cause resentment in joint after start of rehearsal (6)
I believe the answer is:
rankle
'cause resentment' is the definition.
(I've seen this before)
'joint after start of rehearsal' is the wordplay.
'joint' becomes 'ankle' (ankle is a kind of joint).
'after' is a charade indicator (letters next to each other).
'start of' indicates taking the first letters.
The initial letter of 'rehearsal' is 'r'.
'ankle' after 'r' is 'RANKLE'.
'in' is the link.
(Other definitions for rankle that I've seen before include "Eat into and cause resentment" , "Gnaw away at" , "Nag" , "Chafe" , "get up your nose" .)