By agreement, the firm gets a politician to do something (7)
I believe the answer is:
compact
'by agreement' is the definition.
'compact' can be an answer for 'agreement' (compact is a kind of agreement). I am unsure of the 'by' bit.
'firm gets a politician to do something' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'gets' means one lot of letters go next to another.
'a politician' becomes 'MP' (Member of Parliament).
'to' says to put letters next to each other.
'do something' becomes 'act' (to act is to do something).
'co'+'mp'+'act'='COMPACT'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for compact that I've seen before include "The powder-box is closely packed" , "Make denser, agreement" , "Neatly packed" , "Close - agreement - make-up case" , "Tightly grouped" .)