It's arrogant of an MP to ring us at the office (7)
I believe the answer is:
pompous
'it's arrogant' is the definition.
(I've seen this before)
'an mp to ring us at the office' is the wordplay.
'to ring' becomes 'o'.
'at' says to put letters next to each other (I've seen this in other clues).
'the office' becomes 'po' (I can't explain this - if you can you should give a lot more credence to this answer).
'mp'+'o'+'us'='mpous'
'mpous' after 'po' is 'POMPOUS'.
'of' is the link.
Can you help me to learn more?
(Other definitions for pompous that I've seen before include "Affectedly self-important" , "Grandly self-important" , "Puffed up with vanity" , "Arrogant" , "Grandiose" .)