Mother gets twitch after cur becomes opinionated (8)
I believe the answer is:
dogmatic
'opinionated' is the definition.
(I've seen this before)
'mother gets twitch after cur' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'gets' says to put letters next to each other.
'twitch' becomes 'tic' (tic is a kind of twitch).
'after' says to put letters next to each other.
'cur' becomes 'dog' (I've seen this before).
'ma'+'tic' is 'matic'.
'matic' put after 'dog' is 'DOGMATIC'.
'becomes' acts as a link.
(Other definitions for dogmatic that I've seen before include "Assertive, overbearing" , "Inclined to assertion; overbearing" , "Opinionated" , "Giving opinions in arrogant know-all way" , "Stating opinions as if unquestionable" .)