Being disquieted, perhaps, setter might become angry (5)
I believe the answer is:
irate
'angry' is the definition.
(irate can mean angry or annoyed)
'being disquieted perhaps setter might' is the wordplay.
I cannot quite see how this works, but
'being' could be 'rat' (rat is a kind of being) and 'rat' is found in the answer.
'setter' could be 'i' (the person that set the crossword) and 'i' is present in the answer.
A single letter 'e' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'become' is the link.
Can you help me to learn more?
(Other definitions for irate that I've seen before include "Extremely cross" , "Angry, enraged" , "Magical rod" , "Wild" , "raging" .)